I have a Realm, and when I have a command block which executes the command 'spreadplayers 0 0 200 500 @p', it teleports them to a random location in the world, but instead of teleporting them to a random location on the surface, it teleports them to high up in the air at y coordinate 256, meaning the players always end up falling to their death

I attached a screenshot showing the result of executing the command, as you can see the player ends up teleporting high above the clouds