This bug was also reported for the windows platform (MCPE-141713) and is reported as fixed. However this bug is also present on the Xbox platform and is not fixed.

My survival world is from before the cave and cliffs update came out.

World seed: 1924762711
Game mode: Survival
Difficulty: Hard

Steps to reproduce in survival mode:
1) Enter the end
2) Defeat the ender dragon
3) Leave the end
4) Re-enter the end

A second obsidian platform is constructed on top of the already existing one.

Important to note is that this bug seems to only exist for worlds that are made before the cave and cliffs update. I put a lot of time and effort in this survival world I made and re-creating it in the new update does not sound reasonable to me.

I tested this by creating the world again in the 1.19.2 update and was not able to reproduce it. So it would only be possible to reproduce if the world was made before the cave and cliffs update...

Update...

It seems I was wrong about it only affecting worlds created before the cave and cliffs update. The issue is that the game generates the platform at the wrong height. This is from the wiki...

"Obsidian platforms generate at coordinates (100, 48, 0), mostly far away from the island, making it tough to get there. Players who enter the end spawn at coordinates (100, 49, 0) and the other entities that enter the end spawn coordinates (100.5, 50, 0.5), in the middle of and 1 block higher than the platform."

So based on my testing the player is treated like other entities when entering the end after the Cave and Cliffs update. The reason my world gets the double obsidian platform is because before the update the platform was generated at the correct height being (100, 48, 0). After the update the platform gets generated @ (100, 49, 0). I updated the bug report title to reflect the actual issue.