The bug
When a ghast fireball directly hits the player, the fireball does not catch the player on fire. This has happened for a long time, and is probably not a bug, but it is inconsistent with blaze fireballs.
MC-176741
Ghast fireballs don't set the player on fire
Resolved
Works As Intended
12
(Unassigned)
1343496
Confirmed
Entities
1.15.2, 20w13b, 20w14a, 20w18a, 20w20b, ..., 1.20.5, 1.21, 1.21.1, 1.21.2 Pre-Release 3, 1.21.3
Retrieved
Can confirm. A direct hit from a firball does not set any entity on flames.