Update from [Mod] GoldenHelmet:
Based on this report and duplicates documenting the same problem with images, this issue appears to affect all of the mash-up packs made by Minecraft that use higher resolutions than the vanilla textures. See especially
In the texture packs developed for version 1.16.10 (prior to the current one), there is a bug in the texture of piglins and zombified piglins. the piglins are badly assembled and in the zombified piglins they are pigmen. but this only happens in external texture packs not the original ones from the game.
Probably this happens because, in the old textures the one side was reflected in the other but they had to make the change for the texture of the brute piglin because their model is not symmetrical