The most common interpretation of the falling rules that I've seen online is that falling occurs instantaneously, with no opportunity to do anything beforehand unless an ability says otherwise. For instance, if you use Flying Kick, you Leap or High Jump or Long Jump then Strike then fall, and you would not otherwise be able to Strike before returning to the ground.
But in the Fly action, it says "If you're airborne at the end of your turn and didn't use a Fly action this round, you fall."
I've been assuming that this only refers to when you're airborne due to the Fly action and then end your turn without using the Fly action. But considering this rule in the Fly action describes what happens if you don't Fly, that got me wondering: What if this is how it works for any creature that doesn't Fly, including those that didn't Fly to get airborne in the first place?
This would allow creatures to use their full 3 actions before falling. This would address a lot of weird rules interactions, such as not being able to use Leshy Glide or the gliding rune unless you start more than 500 feet in the air. It would also address the weird situation of a creature with a fly Speed being pushed off a cliff and instantly falling 500 feet purely because the creature isn't Flying at that time.
It would also recontextualize abilities like Flying Kick, the jump spell, and the like. Instead of delaying when you fall, those abilities would be making you fall sooner, enabling you to return to the ground quickly so that you can use ground-based actions you wouldn't be able to do while airborne.