Stray cats spawn under floors in half-blocks

Stray cats are spawning inside buildings underneath half-block flooring, in the half-block of air between the ground and the floor.

What I expected to happen was...:
Cats requiring a full block of air to spawn and therefore not being able to be trapped under floors.

What actually happened was...:
Cats are spawning in half-blocks, making it very difficult to track them down. I have torn up my entire floor searching for the source of the meowing.

Note:
Very easy to fix by player (e.g. using solid blocks as flooring instead of half slabs), but it seemed like this wasn't supposed to be happening. Not sure if this is actually a bug or a feature. The cats are fine even just staying under the floor, and they behave normally when dug out.