Hostile mobs other than Warden spawning in & around Ancient City

I'm exploring an Ancient City on Java 1.20.4 Mac OS and am finding monsters within 40 blocks of the city and inside. I also found a glow squid.

What I expected to happen was...:
I did not expect hostile mobs to spawn in (other than the Warden)

What actually happened was...:
A skeleton spawned inside the City, and several zombies/skeletons/creepers spawned within 40 blocks of the city limits

Steps to Reproduce:
Spawn Warden near the outskirts of an Ancient City

Warden does not despawn or "dig" because it senses mobs