Structures do not respect blending and biomes

I tried updating my world from 1.14.2 to 1.18 and when I reached the border between the new and old generation I found a mineshaft in an iceberg, and I was like this: ._.

So I tried to verify something, I copied the same seed from my world and generated a world in 1.18 with that seed, I went to the same coordinates where I found the mineshaft on the iceberg and I found a mineshaft from the plateau and arrived to the conclusion that the structures of 1.18 are generated in blending

Coords: -1030 82 -943