Ghasts don't aggro unless you're at the exact same height they are flying

The bug

Ghasts cannot see you until you get near eye level with them. I've only noticed this with the new mob AI update in the latest snapshots, so I'm guessing the ghast has the same problem that all the other new AI mobs have: they can't see you too well along the y-axis. When you get almost eye level of the ghast, it will shoot.

Update: Tested in 1.14.4: They only aggro if you're on the same level, but once they're aggressive they'll shoot you from any height

Code analysis

Code analysis by [Mod] Sonicwave can be found in this comment.