It's about the circumstances. Have they changed? The outside voices will still be there and whatever assurances you get from the young Miller, it's really hard think you've got a guarantee that the same problem doesn't rear it's head.I hope he comes back, but at least as employment is concerned once an employee is out the door, it doesn't matter if the business gives them a decent counter-offer. Once they have made the decision to leave they're usually gone within 1 year. In his situation this could be different if he made the decision because of outside pressures and has decided to make his own decisions in coming back.
It would be a tough call for BU and difficult to execute smoothly over the course of his career.