Cave generator won't cut through crimson_nylium and warped_nylium, leading to lots of floating nylium

Flying around the nether, I noticed a phenomenon similar to MC-16132. The cave generator seems to consider nylium different than netherrack, leading to lots of floating blocks when you're flying around.

Check out these areas in seed 3734647252753065699, or look at the attachments.

Crimson Nylium:
/tp 1098 64 505

Warped Nylium:
/tp 358 61 87