The bug:
I have a world from pre-1.18. It is a survival world with cheats, and I have explored ~4000 blocks around spawn. Then, when I updated the world to 1.18, I used the /locatebiome command to locate a specific biome. It turned out to teleport me to a chunk that I have already been to, in previous versions. That means the actual biome at the coordinates is different from the biome shown from the /locatebiome command.

Expected outcome:
The result from the command should show a biome with the correct set of coordinates.

How to replicate:
1. Start a new world in any of the pre-1.18 versions.
2. Load around 100 chunks around world spawn. 
3. Then, load this same world in 1.18.2.
4. Use the command /locatebiome and search for a specific biome. (In my case, it was a Flower Forest).
5. Chances are, the shown coordinates will be on a chunk you've been to, and the actual biome is different. (Shown in the attachment below. It is clearly a forest biome, but the coordinates say it is a flower forest, and it is 0 blocks away. World seed [-4358244966102569802], this chunk is loaded pre-1.18)