Looks like Mojang has improved some of the mobs' hitboxes last snapshot, but some still need to be adjusted, like skeletons. This was probably in the last snapshot, but I've noticed it in this one. The zombies' hitbox has been adjusted so it is bigger, to fit the zombie model, but the skeleton is unchanged (I just noticed that zombies and skeletons are actually slightly taller than the player). The zombies and skeletons are the same height, and slightly taller than the player, so it wouldn't make sense to change one and not the other. This is the same issue with villagers and witches, as in my last report.