Undead mounts (while ridden) don't drop 10XP when killed, this is unlike chickens that spawn from chicken jockeys

Camel husks, skeleton horses, zombie horses and zombie nautiluses will never drop 10XP when killed while being mounted by a hostile mob, this is inconsistent with chickens that spawn as part of a chicken jockey, as they will always drop 10XP when killed.

Steps to reproduce the issue:

• Summon any of the four undead mounts with their hostile riders, kill the mount before killing the rider.

Expected result:

• If the undead mount is being ridden, it should drop 10XP like a ridden chicken from a chicken jockey.

Actual result:

• It will drop 1-3 XP always.