The bug
When a spawn egg is used on a snow layer, the mob spawns an entire full block too high, as though the snow layer were a full block. This is a general issue for all blocks that are less than a full block high.
How to reproduce
Place a snow layer
Use a spawn egg on it
→ ❌ Mob spawns one block in midair
[media]
Is is not just snow it also affects every block that doesn’t have a collision box like tall grass, carpet, sapling, rails, flowers, all types of torches. On bedrock the mobs are always spawned next to, above or below the block depending on which side you are aiming while on java they always get spawned at the position of the block when aiming at these block this causes the mob to be spawned too high when aiming at the top side on bedrock. On java it also used to work like it currently does on bedrock, but it was changed on java, I belive it was 1.13 where it got changed.