Chicken jockey have same movement speed as a single baby zombie's movement speed in 1.13, after 1.14 update, the chicken jockey now using the chicken's movement speed, and more slower, this is making them more useless than baby zombies without riding chicken.
MC-271156
Chicken jockey no longer uses baby zombie's movement speed
Open
4
(Unassigned)
Community Consensus
Mob behaviour
Minecraft 18w43a, 1.20.5, 1.20.6, 24w18a, 24w19b, 24w20a, 24w21b, 1.21 Pre-Release 2, 1.21 Pre-Release 4, 1.21
Retrieved
Can confirm, relates to MC-153840.