While I searched and found this same issue resolved earlier, I found a amethyst cave above the ground in a village in the latest snapshot.
Seed: -6173873852370967229
Coordinates found in screenshot
Environment
Windows 10, Java, Snapshot 21w03a
MC-212194
Amethyst caves Still spawn outside
Resolved
Duplicate
0
This appears to be a duplicate of MC-203636, which was later resolved as, "Works As Intended". Please see the parent ticket for further details.