Baby drowned jump on a chicken to create a chicken jokey but it will diretly dismount it even tho there is no water above the chicken head.

This is only a issue if the baby drowned spawn in water (naturaly spawn).
The baby spawn in water, he teleport on the chicken and automaticly dismount it because I think the game still think he is in water even tho he is not anymore.
If you spawn a baby drowned on air with a command he will jump on the chicken and will continue to ride the chicken like normal.