Considering this is a change in API behavior, this is a bug.

entity.getNearbyEntities and world.getNearbyEntities use the
public List<Entity> getEntities(Entity entity, AxisAlignedBB axisalignedbb)

{ return this.a(entity, axisalignedbb, IEntitySelector.d); }

This Entity Selector excludes spectators. This creates a change in behavior (unable to get nearby spectators when you need to) of the API, and also inconsistency between entities reported from the world list vs location selection.

The API should be restored to include them, and add a boolean as a new api method to include or exclude them.