I believe this problem has been fixed since world generation was changed in 1.18.0. Please mark this as resolved.

Old Description(03/27):

Most world seed values have a biome boundary at XZ 0.
This will most likely generate a river in XZ 0 in most worlds.
It seems to exist in Java Edition, but it also exists in Bedrock Edition.

Some seed values are not generated, but there is something wrong with the biome selector because they are too likely to be generated.

The seed value for seeing Swamp and river is "Glacier"(not "falco").

Deleted because there was a screenshot with the same seed value. I'm sorry it's hard to understand.

New Desc(04/21):

 You can see most seed values without having to enter these seeds. Biome boundaries can be created, not just rivers. This is unlikely to be normal as it occurs with almost all seed values. Since rivers are likely to be generated at the biome boundary, I think that the reason why rivers are likely to be generated at XZ 0 is that biome boundaries are likely to occur at XZ 0.

Steps to Reproduce:
1.Enter Seed bot 'falco' or 'Glacier' to Create new world.
2.Command '/tp 0 80 0' to Teleport to XZ 0 Pos.
3.Please look at biome border / river.

Observed Results:
A river or biome boundary is created in the biome.

Expected Results:
It should be generated as the correct biome form (sorry, I don't know how to explain it).