This issue is still there in the snapshot 21w37a
This bug is still present in 1.17.1 and 1.18.
Yes it can be reproduced in 21w18a if u are on a world with extended height, that is, a world with the caves and cliffs preview datapack. I have tested.
The end generation was tweaked in this version by mistake, so the unloaded parts of the end have been generated when u opened ur 21w11a world here
Also present in all 1.18 experimental snapshots and 21w37a