Using spawn eggs on partial blocks can spawn the mob too high

The bug

When using a spawn egg on the top face of a short block (tested with trapdoors and carpets), the mob will spawn on top of the block above the targeted block, instead of on top of the targeted block itself.

To reproduce

1. Place a stack of two carpets on the ground
2. Try to spawn a villager on the bottom carpet

Observed behaviour

The villager spawns on the top carpet

Expected behaviour

The villager would spawn on the bottom carpet (i.e. the targeted block surface)

Notes

Adding more carpets won't cause the villager to spawn even higher

Screenshots