You're meant to restrict it when appropriate, yes.
The relevant part of the rules is just a little after your quote:
If you want to move more than one zone (up to anywhere else on the map), if a situation aspect suggests that it might be difficult to move freely, or if another character is in your way, then you must make an overcome action using Athletics to move. This counts as your action for the exchange.
-- Fate SRD, "Conflicts - Movement"
I can see one of two cases here:
- the mook's action in this exchange could have been done equally well in either zone, and you realized afterwards that you could have repositioned them. In that case, when there's nothing else stopping their movement they can move after their action.
- the mook's action in this exchange needed to be done in one particular zone - like, there's a door there for them to lock - and you wanted them to move afterward. In that case, the need to take action on that specific zone is probably making it difficult to move freely, unless the action itself is taking place on a zone barrier - like, there's a door for them to unlock. Whatever they're taking action on is, effectively, an aspect saying otherwise or a character in their way.
...at least assuming you're playing zones in line with Core, and not using some variant that requires city-block-distance tactical thinking. There are a lot of Fate variants which will show examples of play that have, say, index cards laid out like a weirdly squashed grid map but you shouldn't take that to mean that you can just lay out a tactical grid of arbitrary size with 5-foot zones and have everything still work.
It has to do with the roles of zones as Fate Core conceives of them.
The first rule of tactics club is don't join tactics club.
Generally speaking, a conflict should rarely involve more than a handful of zones. Two to four is probably sufficient, save for really big conflicts. This isn’t a miniatures board game—zones should give a tactile sense of the environment, but at the point where you need something more than a cocktail napkin to lay it out, you’re getting too complicated.
-- Fate SRD, "Conflicts - Zones"
I like to talk about Fate using cinematic analogies, so: think of a zone in the Core sense as a shot in the movie, a camera at a fixed angle and everything it can see. Cameras are set up to catch all the important bits of a scene and there are two rules for each camera:
- first, when you cut to a camera the audience shouldn't be disoriented and be able to recognize where the shot is coming from
- second, when you cut to a camera the audience should be able to anticipate what the footage shot from that cut is going to be about; this doesn't mean that they're right, but that you're able to play off their anticipation
If you can say that about all your zones then you're good, because zones exist to organize the space where a conflict is happening in a cinematic sense. Who should be in each shot and what should they be doing when they've got the spotlight?
(In the rulebook's reference example, the zones can be summarized as "warehouse floor and entrance, about people getting in, leaving, or being dropped in the drink", "warehouse floor and ladder, the main location of interest with a possible struggle for the ladder", and "catwalks, about taking advantage of or being deprived of the higher ground".)
So the free movement of one zone is a restriction about which shots you can be in; one zone is as far as you can move into a shot without it being confusing that you got there. This is consistent with a later principle:
Sometimes it just makes sense that your character is doing something else in conjunction with or as a step toward their action in an exchange. You quick-draw a weapon before you use it, you shout a warning before you kick in a door, or you quickly size up a room before you attack. These little bits of action are colorful description more than anything else, meant to add atmosphere to the scene. [...] You shouldn't require any mechanics to deal with that.
-- Fate SRD, "Conflicts - Free Actions"
But converting zones to elements on a strict tactical grid breaks both of the cinematic principles of abstract zones.
- Zones on a tactical map exist to take up space, not be distinct and recognizable. Usually they're just referred to by grid coordinates.
- Action on a tactical map is much more about the relative positioning of the characters than it is about any characteristics of the zone.
If your group understands tactics but not cinematic action you may not really have a choice in the matter, but when you make that conversion, well...
The second rule of tactics club is if it's your first time at tactics club, you have to hack.
When you change the idea of what zones are, "move one zone for free" stops making sense, because it's not talking about the same thing. Motion isn't a cinematic concern anymore, it's a tactical concern, and it's not being constrained to make the movie make sense because there is no movie.
Instead, motion should fit the needs of a tactics game. To understand those needs let's have a look at a popular small-unit tactics game, XCOM, and see how its motion works, what needs it meets, and how that might be adapted to Fate.
- Every turn you get a tactical move and then an action, which can be making an attack, using a consumable, or making a second tactical move.
- Attacking ends your turn and you can't move afterwards.
- Melee units have better maneuverability than ranged units of the same relative power.
Taking a move and then an action is because traversing a tactical map is fun and sometimes challenging, and also necessary as circumstances demand it. Fate already has some guidance on movement over larger maps:
In games with quite a few zones, you may want to allow characters to sacrifice their turn in order to move a number of zones equal to their Athletics or to remove a number of physical obstacles equal to their Physique. Fast and strong characters want to be fast and strong, but rolling dice isn’t always the best way to represent that in Fate.
-- Fate System Toolkit, "Zones - Moving Through Zones"
If you're working with a sufficiently large tactical map that even a peak Athletics character wouldn't be able to get across it in one go, that's a pretty good model for everybody's tactical move. I'd maybe mix it up a little bit, have you cap out at Athletics total zones or Physique total terrain difficulty (vanilla 0, common unaspected obstacles at 1 or 2), whichever comes first. If you spend your entire go moving, I'd suggest making the second tactical move a rolled tactical move, so that the higher-Athletics people have a chance to get a boost going forward.
Stopping immediately when you attack is because making attacks is usually what wins you tactical encounters, and exposing yourself to a counterattack from your attack position is the price you pay for taking a chance on winning. So it can probably persist in Fate - you can't take your tactical move after you act. Though it's also a fairly common element of tactics games to make "move after an attack anyway" a progression upgrade.
Melee units outmaneuvering ranged units is kind of the balance to having an arbitrary tactical grid where otherwise ranged units might be able to pull back forever and still keep firing. It's a concern for Fate if you're keeping the ability of a unit to Fight others only within its zone - in that case, if you're constructing all of the tactical options yourself, you can just make a melee loadout also give a bonus to Athletics and Physique for purposes of the tactical move. Alternately, you could say that Fight comes with a free half-tactical move, round up, to help melee fighters close in.