Baby animals and villagers are getting adult hitboxes after log out/in

All babies are getting their adult hit boxes when you log out and log back in.

Simple test case:
Get a newly created baby animal/villager in the situation shown in the picture. The baby is fine and does not burn. Log out and in, the baby will burn to death.

This seems to also be the reason for baby animals glitching through walls when logging back into the game.