This behavior was introduced in 26.2-snapshot-4.
I turn off the "Spawn Monsters" game rule, but it does not prevent monsters from spawning.
MC-307754
Monsters now spawn regardless of the "Spawn Monsters" game rule
Resolved
Fixed
2
(Unassigned)
Confirmed
Expansion A
Very Important
Mob spawning
26.2 Snapshot 4
26.2 Snapshot 5
Retrieved
Can confirm as of 26.2 Snapshot 4