Steps to reproduce

1. Turn off mobgriefing. (Set to false.)
2. Summon a ghast.
3. Let it shoot you.

Expected result

You do not get set on fire. (Note that some hits will not set you on fire because they do not damage you at all, but that is a separate bug that can be worked around by changing position slightly between shots: see MCPE-78714. You do get set on fire by damaging hits).

• In Java you do not get set on fire by ghast fireballs with mobgriefing off.
• The minecraft:explode component in fireball.json includes "fire_affected_by_griefing": true,.

Observed result

You get set on fire by ghast fireballs.

• If you set fireballs to be summonable with a behavior pack and summon them on yourself with mobgriefing off then you do not get set on fire. So, I hypothesize that ghast attacks are hard-coded to set mobs on fire and that that is not affected by mobgriefing.