Piglins can somehow be repelled by soul fire (but not zombified piglins) through walls although they can't visually see soul fire through walls.
How to Reproduce
Build a wall with the center being hollow
Summon piglin
Turn on subtitles
Place soul fire
→ ❌ Piglin retreats appear
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Comments 3
This is intentional for hoglins and warped fungi, see MC-172399. This might also be intentional for respawn anchors and nether portals if they have an odor that hoglins dislike.
I think its more of a feature than a bug. sure, it doesn't follow real-life logic, but these are creatures from another dimension, so you wouldn't really expect them to follow all the rules of the over world. perhaps they share a psychic link with the fungus, idk.