So while I was in my creative world testing/building in the latest snapshot, 19w08b, I've stumbled upon a weird mob spawning behavior that's done with mob spawn eggs.

I've tested every type of mobs that are spawned with their egg and spawned each everyone individually (with the egg, not spawned in through commands.) and everyone single one seemed to be misplaced down into the block when they're supposed to be in the water stream not spawned into the block. They also don't seem to take suffocation damage the moment the mobs heads are collided into the block as they're falling through.

Here is one of my screenshots that I took for evidence for y'all to see: