Guardian not spawning in existing generated ocean monuments

I've seen the changelogs in the new snapshot 20w22a and it fixed the mob generation in structures. It works fine in my existing nether fortresses and illager outposts, but it doesn't seem to fix my existing ocean monument. Still, it doesn't spawn guardians. I've drained the interior of the monument and mobs like spiders and creepers seems to spawn inside. I've also built a conduit above of the temple.