Some passive mobs that do not naturally spawn or despawn are still included in the passive mob cap

On the debug screen, the C value under the mob caps counts several passive mobs which can neither spawn during the spawn cycle nor despawn:

• Allay

• Bee

• Happy ghast

• Sniffer

• Tadpole

Allays generate as part of a structure but are not part of the passive mob spawn cycle, so there is no reason for them to be included in the mob cap.

I tested it in a superflat creative world by using /kill @e[type=!player] and then spawning a bunch of sniffers. No new passive mobs spawned.