Can reproduce this and it seems to be one of the biggest problems since then all player data gets completely swapped to a first-time player save including blank copies of ender chest containers.
Can reproduce this even without third-party mods installed that try to tweak it, And it is kinda annoying in reality when this appears to be more of an vanilla issue than what older versions can produce.
Can reproduce this with my iPad and my linux machine - the chunks in java are completely broken unlike bedrock's end.
Confirmed, this makes server performance much worse than the previous version 1.20.1.