/spreadplayers spawns you in the floor, this causes you to fall through 1 block thick floors upon spawning in, and is generally very silly.
Steps to reproduce: run a valid spreadplayers command
Observe: floorness existing in your legs
Expected result: being on the ground
Observed result: being in the ground
The way it used to work is it would spawn you one block above the highest block at the x and z coordinates it teleported you to, now it spawns you in that block
I see the same issue. We use /spreadplayers command blocks, and this broke several systems now that players spawn within the block.
This issue is still open as of 1.19.80.02.