The bug
Killing an zombie piglin in survival during their hostile state causes them to drop xp even when the doMobLoot gamerule is set to false.
To reproduce
disable
doMobLootSpawn a zombified piglin
Go to survival and kill the zombified piglin
→ ❌ They're dropping experience even ifdoMobLootis set to false
Can't seem to reproduce anymore, even in pre-release 8.