It is not a Problem for Undead Mobs in general, its more likely that this happens because the Wither Skeleton and Zombified Piglins are Variants of Zombies and Skeletons that never had their Functionality of Burning in the Daylight removed as for them, the Functionality didn't do anything in the first place as the two are Immune to Fire and they also don't even show Visual Fire when in the Sunlight. Thats atleast until they added Helmets breaking in the Sunlight.
The Husk isn't completely immune to Fire so it has a unique Script that makes it only immune to Sunlight which also prevents this Bug to work on them.
Pixelpiekser
It is not a Problem for Undead Mobs in general, its more likely that this happens because the Wither Skeleton and Zombified Piglins are Variants of Zombies and Skeletons that never had their Functionality of Burning in the Daylight removed as for them, the Functionality didn't do anything in the first place as the two are Immune to Fire and they also don't even show Visual Fire when in the Sunlight. Thats atleast until they added Helmets breaking in the Sunlight.
The Husk isn't completely immune to Fire so it has a unique Script that makes it only immune to Sunlight which also prevents this Bug to work on them.