Even if the world-gen had back to 21w05b, but the world-gen of "Floating Islands" still looks like "AMPLIFIED" world, just like 21w06a to 21w14a.
- Create a world whose the "World Type" is "Floating Islands" in 21w05b
-> There will be many floating islands just like the outer islands of the end.
- Open the world in 21w15a.
- Fly some distance in creative mode.
-> You can see a huge weird terrain just likes the far land.
Yes, the huge terrain is generated in 21w15a, when you create a world whose the "World Type" is "Floating Islands" in 21w14a, the terrain will be also looks like a "AMPLIFIED" world, but it won't happen to 21w05b or earlier version.
The picture 20210417004420 is the terrain in 21w05b(left) and 21w15a(right).
The picture 20210417005559 is the terrain in 21w14a.