Actually, I have a rather basic question... When you fall, do you fall immediately? Isn't it that you have to "use" your movement action to fall (at falling speed, not at your land base speed of course), just as you have to "use" a move when jumping a distance?
It has not much to do with the original question, but I am not sure.
Does it make a difference if you fall outside your round? For example, if someone bullrushes you down a chasm, do you start falling immediately or do you start counting the covered fall distance on your initiative? That obviously has to do with the abstraction of rounds, but it could be important to know if some of your allies have any chance to try and grab you before you are gone.