Potion effects don't affect player FOVs when the player is spectating an entity

The Bug

While a player is spectating another entity, such as another player, the spectator's FOV will not be affected by either the spectator itself or the spectated mob's speed/slowness effects.

To Reproduce

1. /summon minecraft:zombie ~ ~ ~ {ActiveEffects: [\{Id: 2b, Amplifier: 10b, Duration: 2147483647\}]}
2. /effect give @s minecraft:slowness 1000000 10 true
3. Spectate the zombie.
   • Notice how your FOV is not changed at all.