Maybe not "normal" but not a bug; "floating islands" islands are considered to be a feature of world generation and have always been present (the same seed in versions as old as 1.7 should give the same terrain, or close to it as no significant changes have been made since then (the changes to oceans in 1.13 may have affected the seed locally); at least, I haven't seen reports of chunk walls due to terrain changes):
Is this even normal? I don't think it is
Maybe not "normal" but not a bug; "floating islands" islands are considered to be a feature of world generation and have always been present (the same seed in versions as old as 1.7 should give the same terrain, or close to it as no significant changes have been made since then (the changes to oceans in 1.13 may have affected the seed locally); at least, I haven't seen reports of chunk walls due to terrain changes):
https://minecraft.gamepedia.com/Terrain_features#Floating_island (as seen by this example from 2012 they are not new, and were more common prior to Beta 1.8 due to most biomes having more varied terrain. I occasionally see them in first world, in 1.6.4, mostly a few blocks, sometimes with trees)
TheMasterCaver's First World - possibly the most caved-out world in Minecraft history - includes world download.
TheMasterCaver's World - my own version of Minecraft largely based on my views of how the game should have evolved since 1.6.4.
Why do I still play in 1.6.4?
Yeah, this sort of thing happens from time to time.
That's been a thing since I started playing (1.2.5) and I saw it again today (1.16.3).