Duplicated mineshafts with new cave generation

Load up seed -709494128138866206 in 1.17 at let the chunks load up at spawn. Open up the world in 21W44A, there is a mineshaft directly below the immediate chunks. It appears twice, once above Y= 0 and again below 0

/execute in minecraft:overworld run tp @s 159.94 19.05 390.78 -141.76 13.20