In my new world, the spawn was on a specific block. I made sure to mark the coordinates with F3.

After gathering some resources, I made a compass. The strange thing is that it points to another block in another chunk.

I tested it creating a new world (different seed) and noticed the same compass behavior. I entered Creative, went to the End, killed the dragon and, to my surprise, the return to the Overworld was in a different location.

I have some screenshots to show the locations:

• Spawn when creating the world: Crimsom Plank
• Compass pointing: exact center of Warped Plank
• Return Spawn (End portal): Black Glazed Terracotta

I don't know the seed of the world I'm playing in (Hardcore), but I've tested it on other random seeds to test it.

Seed of screenshots: 8090619227927263857