This bug was present in the previous snapshot as well. I thought it was related to the generated structures not spawning mobs bug, which the change log states was fixed, but my witch farm is working just fine.
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MMK21
galaxy_2alex
We're tracking this in MC-186096.
migrated
I think the only structures that still haven't been fixed in 20w22a are the ocean monuments still. The other structures in my world pregenerated before this update are valid structures. i'm stuck on 20w20b in my world 1.16 world because my ocean monument is still spawning guardians. Newer versions, it doesn't spawn them.
Duplicate of MC-184740