On nether-biomed superflat or buffet worlds hoglins change to zoglins right after spawning.
This is probably due to hoglins checking dimension instead of biome when turning into zoglins.
Same issue as for piglins, described MC-174329
MC-177487
On nether-biomed superflat or buffet worlds hoglins still change to zoglins
Resolved
Invalid
1
This is technically because the biome is a nether biome, but not the dimension. To have hoglins not turn into zoglins you will have to change the IsImmuneToZombification tag to 1.