The whole "left a blood splatter on the enemy sniper's head but he didn't get headshot" as well as "took a shot and missed but after you unscope the enemy sniper takes your headshot and dies" are both practically tropes by now.
I know CS:GO's hotboxes were updated with more accurate shapes like cylinders instead of cubes, so that may be one reason why you dont see that weird "blood but no hit" thing. AFAIK the blood appears if you hit any part of the model even if there is no hitbox on that specific area, like engineer's cock.