I spawned a horse in a 1x1x2 hole and it floated. Not much more to tell.

What I expected to happen was...: 
The horse to be on the block I spawned it on.

What actually happened was...:
The horse ended up floating a block above where it was spawned. The horse would've been on the ground with a 1x1x1 hole, but if its any bigger it just ends up a block above where it was spawned, like its walking on them. It works with all horses, the regular spider, polar bears, illiger beasts, etc. I assume its that their hitbox is bigger than the hole. Other mobs that can fit in 1x1x2 spaces spawn fine.

Steps to Reproduce:
1. Make a 1x1x2 hole (x,z,y)
2. Spawn a previously mentioned mob on the bottom block.