This bug/feature was found in 1.17.11 with all experimental features enabled, including Caves & Cliffs.

As the title decleared, Please find all emeralds in this picture: 

If you have found them all, you could have found 6 emeralds - merely on the surface of this terrain. There might be more emeralds next to them: 

Yes, you have seen 8 emeralds in this chunk!
But in this following picture, the same world but no experimental features, your dream that it wasn't a bug would come to a dawnbreak:

N-O-T-H-I-N-G-!
Apperantly, this could be a bug of experimental features. This example could be re-played by these information below.

Seed: 1817903200