Glitches and exploits in Heroes.

Well, I think it's just a useless glitch... You still can't move during it.
And by the way, this happens not only when a hero ends his turn in a garrison... it happens anywhere...

It's not just in the 5th game. I know of a similar thing in the 3rd game...
If a hero is running on "penalty" terrain, he often has one or two steps left, but he can't move anywhere. In such cases, to prevent the message "heroes can still move" from popping up, I double-click the hero in any direction, and his "movement" is exhausted.