Terrain blending of old worlds places dirt and stone on icebergs in frozen oceans

When an old world is upgraded, and that world has icebergs at the edge of the blended area in a frozen ocean biome, the icebergs get dirt and stone placed next to them.

To reproduce:
1.Make a creative world in 1.17.1 with seed 16. Save without moving.
2.Load this world in 1.18-pre1 (or version being tested).
3.Fly around the edges of the world around the frozen oceans. -> Icebergs have stone and dirt placed on them at the blended edge.

Attached screenshot was taken with seed 16 near -97 -270.