Not sure if this is a feature that I missed, but when I ported into the nether, I noticed a large number of Skeletons (not wither skeletons) in the nether.
They were amongst the fossils in areas with soul soil.
Comments 4
See MC-2716. Intended game behavior.
Skeletons are supposed to spawn in the soul sand valleys in the nether, see https://www.minecraft.net/en-us/article/minecraft-snapshot-20w06a
This is likely intended because of the bones in the soul sand valley.