How does the skill trick Extreme Leap work?

The skill trick "Extreme Leap" reads:

Extreme Leap [Movement] Your extraordinary leaping ability carries you over great distances. Prerequisite: Jump 5 ranks. Benefit: If you make a horizontal jump of at least 10 feet during your turn, you can spend a swift action to move an additional 10 feet on that turn. Complete Scoundrel, p. 86

So, if a character with a movement of 40 feet takes a move action trying to leap over a chasm of 20 feet taking a 20 feet running start, does he...

a) ...have to make a Jump check DC 10 and use the skill trick "Extreme Leap" to cover the distance over the chasm and has 10 feet of movement left on the other side.

b) ...have to make a Jump check DC 20 to cover the distance and get a bonus move of 10 feet once he lands on the other side.

From the name of the trick and the phrase "your extraodinary leaping abiltiy carries you over great distances" I always assumed the trick adds another 10 feet jumping distance, but rereading the benefit text I am not sure now.

RAW, it’s b, but I agree that that’s surprising and counter-intuitive. I also would have thought a. But now that I read it carefully, I think there is something to b—it’s not quite right but it is handling a situation that a would not, and should be by something called Extreme Leap.

Namely, imagine your character with a 30-ft. move speed hit a DC 40 check to leap a 40-ft. gap. (Presume access to something to count as having a running start, and that the character doesn’t have a standard action available—surprise round, nausea, or just having already used it.) In this situation, without Extreme Leap, their turn ends while they are mid-air, above the gap 10 feet from the edge—i.e. where their 30-ft. move speed ran out. That’s awkward. Someone capable of “extreme leaps” might need movement speed boosts just so they can actually complete them. And that is what Extreme Leap does.

It’s still very awkward though—the movement boost still applies even if you land and are moving on the far side of your jump. This might have been a balance choice—not wanting to force players into awkward choices to trigger their bonus, to make sure the bonus applies often enough to be worth taking—but that feels off. So does the fact that Extreme Leap doesn’t actually help you leap farther; at best it helps the leaps you were already making happen in one turn.

Still, all this does suggest to be that despite might intuitive assumptions, a isn’t the best way to rule things. Instead, I would probably do both a and b here. Well, the wording on the “a effect” should be to reduce the DC by 10 or give you a +10 bonus, but it amounts to the same idea. And maybe that bonus seems high for a skill truck—maybe that’s evidence that they intentionally didn’t do the intuitive thing, and this is why—but honestly, investing in Jump is just a poor choice for most characters, because flight is mandatory by 10th level at the absolute latest. So I wouldn’t worry about that, even if Wizards might have.

• Thank you for your fast and thorough answer. Just to give more context: I am trying to max out my "Sudden Leap" Tiger Claw maneuver to go in for an unexpected full attack. 10 feet extra jump would have been perfect. 10 feet extra move... nah... Apr 2 '20 at 13:26
• I believe it works this way in an attempt to use swift actions instead of saying "once per turn" since a character only gets one swift action per turn. I don't believe there is anything stating that a swift action cannot be used in conjunction/simultaneously with another action, just that it's a free action that can only be taken in that character's turn and only once per turn. Apr 4 '20 at 0:59
• @WannabeWarlock I don’t see how that affects whether this has the effect a or b, or addresses anything in my answer? Apr 4 '20 at 1:54
• Because he could move 10' before landing if he takes his swift action during the move action without any confusion/etc. Apr 4 '20 at 2:02
• @WannabeWarlock I am not following. Do you mean he could move 10 feet more in the air before landing, i.e. have a 10-ft. longer jump? That would be option b, and not what the rules as written support. Apr 4 '20 at 2:07