Age of Empire IV: Stone Wall Tower bug - YouTube
Both stone wall tower and gate mention units can access top of the wall with them, but only stone wall tower can access to the top before it is competed.
Which makes stone wall tower rush so much stronger than it should, as villagers can get on top of the wall to compete the tower. Not much you can do to counter it. Also, can you this trick and del uncompleted stone wall tower to trap opponents on top.