Alright, reading the rules a bit more closely, I think we actually have some help here. It says on page 8:
Caveat : Reacting models are not activating, therefore do not remove fatigue after Repositioning.
There we go. A model that is not activating does not get to remove fatigue.
Also, I think I am starting to agree with your assessment that "Reposition" and
is not the same thing. Page 8 describes that
= Reposition + 1 damage. And then explains that Reposition means "may move 3 inches".
So it seems clear enough really. The word "Reposition" is just shorthand for "may move 3 inches, and if the model is currently activating and ends up not engaged, it may end its activation and recover one fatigue". It only includes damage if it actually shows the icon.
I then have a follow-up question to that. Leo has an ability called Pounce: "When this model declares an attack during its activation, it may Reposition before resolving the attack".
Can he use the "end activation and remove fatigue" effect during a Pounce, to get extra speed?
I.e. move forward 6" for free, declare an attack against an enemy (spend 1 fatigue), use Pounce, move 3" past the enemy, be disengaged, lose the ability to resolve the originally declared attack, then end activation (and recover 1 fatigue)?
As I'm reading it now, I don't see why he couldn't. But the ability says "before resolving the attack", which could be read to imply that he has to stick around and actually resolve the attack he originally declared, which would mean he can only move around his target, not disengage from it... (but it could also just be a timing explanation, not a requirement.)