I am not sure if this is intended or not but piglins and hoglins will take fire damage if they go into fire or lava. I find it weird because piglins and hoglins spawn in the nether. And if a piglin isn't in the nether it zombifies. In the nether the environment is lava and fire is everywhere and those 2 mobs spawn there frequently. So if this is a bug please fix it because it doesn't make sense for a nether exclusive mob to burn in contact with fire and lava.