Blocks under end island respawn after world reload

I was mining out all the obsidian pillars in the end island and made a small end stone bridge which I later destroyed. I booted up the world later and noticed it was still there and destroyed it again. I booted up the world today and the bridge is still there. I went and broke it, left the world, booted it up again and the bridge was still there. The bridge is at Y: 1. I made a copy of the world and swapped out the blocks and it worked with the new block I placed so this bug can be used to duplicate rare blocks like diamond and netherite blocks. To get rid of the blocks permanently I used buttons. I broke a block and put a button in its place and then relogged. I repeated this until the entire bridge was gone.