Adding narrative details to your combat actions without any implications to game mechanics is not considered a called shot, it is simply a stylistic approach to describing battle.
A called shot refers to a method of combat where participants choose the part or region of their adversary's body they wish to strike. On a successful attack to that specific part/region of the body there is additional damage inflicted, the creature is affected by a condition, or there is some other additional negative impact on the creature. Because the effect is more severe, called shots are usually designed to be more difficult to achieve than a standard attack.
The question you are asking can be reduced to:
Should I let players participate in narrating their attacks?
Giving players the opportunity to direct the details of their actions will make them more active participants in the world you have created. It will make the game more immersive, more fun, and you will experience more memorable events in your world and at your gaming table.
If, as you state, there is no change to game mechanics, then you can narrate however you choose without any concerns about balance.
In January I was GMing a game that included 4 players between 8 and 10 years old.
Kid 1: I want to hit the goblin in the pee pee!
Me: Which weapon do you use?
Kid 1: My sword!
Kid 2: No! Use the warhammer!
All kids: Laughing
Kid 1: My warhammer!
Me: Ok, with one or two hands?
Kid 1: Two hands! (more laughing)
Literally 7 minutes of laughter ensue. The kids are literally on the floor. Kids are laughing, adults are laughing at/with the kids. I'm laughing. It's an absolute riot.
Me: You nail the goblin between the legs and he flies into the air, knocking down the five goblins behind him. They get up, and are madder than ever. Now you're in for it!
Kid 1: Yeah!
All kids: shouting, screaming, laughing and imitating the goblin flying back holding his goblinny goobers.
Nothing changed in-game with this hit. Yes I said the other goblins got knocked down, but it was just for narrative flair and had no impact on their movement, actions or anything else. Mechanically, it was just a standard critical hit.
9 months later, the campaign has ended and that moment still comes up not infrequently in conversation between these kids.
How different would it have been if the conversation went like this?
Kid 1: I attack the goblin.
Me: Which weapon do you use?
Kid 1: My sword.
Me: You nail him!
(roll damage and move on to next player)
If there are game-tables that tear through battle scenes, only following mechanics and never adding narrative flair I don't know of them. I'm sure they exist, and I'm sure they have fun, and I have no judgement, but that is not how I have seen anyone ever play the game. Sure there are times when efficiency trumps narration, and each table finds a comfortable balance, but it's always a balance between the two.
The game-table is a collection of players, including the GM. The GM's role is to build the world, narrate the actions of non-player characters and describe the results of player actions based on player input and dice roll. The more input the players give the GM as to the focus of their action, the easier it makes the GM's job of narrating that action.
When a player is specific about their attack it means there is something they want to see happen in the game narrative and the GM should absolutely run with it.