Trying the seed 1728847091 in a world, and travelling to coordinates -217 97 -788 displays an extremely broken Nether Generation, where very little Netherrack generates leaving the two bedrock layers, floating lava, and random patches of magma block.
Cannot confirm in 20w16a, for me this is part of a basalt delta and the area you are showing has basalt. Can you try generating the world again and see if you are experiencing the issue there as we well?
Also have you created the world in a pervious version of the game?