Maxperson
Morkus from Orkus
So, was this expectation about falling damage set at start of play... or even anywhere along the way? Have characters been taking falling damage as normal throughout the game?
Because, while the GM is in charge, they do have some responsibility to be consistent. It they haven't set it forth beforehand, to depart from established pattern suddenly isn't really a great move on the GM's part.
Ideally things are set forth up front. Sometimes, though, you don't expect shenanigans like a player turning his barbarian into Wile E. Coyote. A ruling has to be made on the spot for the integrity of the game(my game).
If something unexpected comes up that I think should be changed, but doesn't break the integrity of the game, I just let it be known that a change will be made for the next campaign.