The /spreadplayers command glitches out in the better together update and always spawns you at build height and drops you down.

Scratch that, it's just in flat worlds, default worlds work fine.
Also I checked with another device it is all flatworlds the other device was an android phone so almost the opposite of the ipad mini I used to find the bug

now when i run the command through execute @a it works in flatworlds but if i do execute @p it Doesn't

the command sends me to the build height if i use set coordinates but relative work fine.