Structure height may change through logout and login of world. I noticed this with a shipwreck first but the while trying to report a different bug this happened.
MCPE-242764
Structure height may randomly change during logo and log into world
Open
1
It is worse than I said. It seems like bedrock is only saving chunks that are built in and not generated. Which could explain why the files are less than 50 mb even though I traveled 600-4000 blocks in each direction in bedrock editor with 96 chunks to be rendered in.