Mob Spawning in structures fails in pre-1.18 generated monuments/swamp huts/outposts

Guardians but also witches aren't spawning in pre-1.18 generated monuments/swamp huts i.e. farms. It is simple to recreate: open up pre-1.18 world with already generated monuments/swamp huts in the new snapshot.

This issue comes to light now this bug was fixed, so i'm not sure if this specific issue came with the first or latest 1.18 snapshot: https://bugs.mojang.com/browse/MC-237986