Raids start without generating illager mobs

A raid started (via Bad Omen) in a village which naturally spans an extreme range of y-levels. Although the "Raid" banner was clearly visible and villagers were reacting as though raided, no hostile mobs spawned and eventually the raid expired.

 

Seed: -1847774017739967810
Coordinates of (a block inside the) village: -375 124 274