Oh well, you're really picking apart some dirty designer secrets now
It would be nice, if the unit gets stuck in a ZOC and then subsequently overruns whoever exerted that ZOC, that the unit gets released (i.e. its AP is unlocked). Sounds natural.
But I can't do that because I don't know for sure whose ZOC it was in the first place. What if there was another unit also exerting ZOC into the same hex? And, for that matter, what if the AP was locked for some other reason, such as crossing a river or entering a mountain hex?
As discussed before, this game design is necessarily knife-edge because it tries to simulate many advanced effects while keeping the mechanics nice and simple. There's bound to be warts like that, or at least I haven't figured out a way to get rid of them completely.