Pressing this just makes you dismount and fall to the ground

yea so I suppose you can change that key as its a keybind :P

Still, the default key could be something else

or mojang could do a normal crouch button which is control and not shift 🙃

One of these options is much more possible to happen though

the most possible is you changing it yourself :)

Wouldn't this be considered a bug?

If I was to install just your mod, and change nothing about it. You'd still fall to the ground?

In this case, you're wanting everyone who uses your mod to either re-bind vanilla keys, or to re-bind your mods descend key...

Add another voice to the side of changing default key bindings. Your default config causes players to get kicked from the server if flying is disabled. Fix your mod please.