Yes, that is normal and every campaign managers have their own decisions and perspective way in selecting participants.
If there is no potential member rank applicant's who applied, managers choose those higher rank than choosing member rank to fill the slot but inactive and probably have spam post.

Let the managers be a manager and I think there is no problem with that as long as the manager's choosing the right one and it is deserving of the slot. (active, reputable, good and regular poster members are deserving to accept).

Probably if you are one of the managers here, you will understand.