Untamed wolves don’t naturally attack skeleton horses, this is inconsistent with other skeletons as they will hunt down skeletons, parched, bogged, wither skeletons and strays.
Steps to reproduce the issue:
Summon a untamed wolf and a skeleton horse.
Expected result:
The wolf would attack the skeleton horse.
Actual result:
The wolf ignores the skeleton horse.
Can confirm - 1.21.11 Pre-Release 1
Steps to reproduce the issue:
Summon an untamed wolf and a skeleton horse in the same area.
Observe the wolf's behavior.
Expected result:
The untamed wolf should naturally target and attack the skeleton horse, consistent with its behavior toward other skeleton-type mobs (skeletons, strays, wither skeletons, bogged, parched).
Actual result:
The wolf completely ignores the skeleton horse.