sounds like your center manager is frustrated and making a poor choice. On the other hand, it also sounds like this woman is putting him regularly in an impossible situation. She comes in, gets ready to run a route. Staffing is done, all the low seniority cover drivers, if any, are waved off. Now she says, I have to go. So he has to scramble and get a cover back in pronto, by which time there are probably going to be missed service on air anyway. OR, does he keep a cover driver until he is sure? If so, and that driver pushes the issue, they could file for their 8 if he is not sure she is going to run the route until after posted starts. OR, does he send a supervisor on the route when she waves off until a cover can be brought in to eliminate the service failures and eat the grievance on that. Maybe he has decided to just eat the grievance for her, as he is going to eat one anyway, and at least knock down the service failures.
I doubt he is intentionally rewarding anyone in any case.