/spreadplayers will always spread players onto a ceiling if there is one.

For the minigame I was making, I was making a map. But, there was a ceiling over it. So when i connected the lobby and the map, and added /spreadplayers to the command block, it always put me over the map, not in it. I don't know if that was intended, or if there is a 50/50 chance, but there is also no Y coordinate in /spreadplayers so if that's the problem, I would like it added.