Glacier of the White Worm terrain.

[Zethanon]

Zethanon was flying over the Glacier of the White Worm when suddenly:

Your mount stumbles while trying to traverse the glacier and knocks you off.
You dismount Zeitana, an ebony griffon with purple pinions.

A character GM in mount would likely be able to prevent their griffon knocking parts of a glacier and 'stumbling', as well as probably recover themselves to where they aren't knocked from mount.

I get the idea that the area is meant to knock riding mounts, say, horses and the like. But for flying there are few things that would be unavoidable, unless it's like the sky is falling and they're getting hit with chunks of ice. I'm putting this in suggestion to as suggest maybe the verbiage be along the lines of the above with flying debris, or the area checks for flying mounts specific and there is no harm no foul.