Hijacking my own ticket: I definitely agree with the several people who have commented below: I'd like this to be changed back! Fun overrides this nit picky way I was suggesting of being consistent.

What I expected: I had reasoned that since the presence of a spectator does not trigger the spawning of mobs, that likewise the presence of a spectator would be insufficient reason for mobs such as skeletons and zombies to hang around in the absence of other players.

What I saw: Mobs that typically would despawn when a player moves out of their radius, were hanging around indefinitely as if my presence was preventing them from despawning.

It seems convenient on the one hand that a spectator can camp out inside an enderman for instance and spy on people who might come along, with that cool shader, or something, but on the other hand it ends up being a giveaway to other players that the otherwise-despawning mob must contain a spectator.