It is definitely a thing. Most of the time game engine doesn't take vertical axis into account. Even without looking in code, you can see it. Every ranged spell has a cylindrical area of targeting instead of spherical. Every AOE is flat. Every creature (even flying onece) is glued to the ground.

I made an experiment once. Just swaping positions of caster and target affects wether spell is usable or not.
[img]https://steamuserimages-a.akamaihd....D44EDAE817DD359532E12AD4DA44992CDB432F3/[/img]
[img]https://steamuserimages-a.akamaihd....87A85FA1E34074F0E0DBFA2143CF82F34D35699/[/img]