Sharp chunk edges when updating to 1.18 RC3

Began a world in snapshot 21W41a – explored a small amount, then updated the world to 1.18 RC 3

The world generation at spawn (-264, 10 in 21W41a) is a completely different biome, so I expected some slight problems with new world generation.

but I did not expect a village to generate OVER icebergs and so many chunk boarder problems. This location is: -1045, 533