Contrast that first link with this:
https://www.youtube.com/watch?v=Y2inY0zT33QI haven't followed closely, so I don't know specifics, but I remember seeing Don about 5 years or so ago doing an accoustic slot opening for another band, and his voice sounded shot. Don even commented on stage during some in-between-song banter that the years of drinking, smoking, and partying had caught up with him. Maybe he was overstating it as part of his onstage schtick, but I took it at face value. If that is all true, it just seems like even with some rehab and coaching, while he could get some of it back, he has lost quite a bit that is gone for good. I am sure that with multiple takes, punching in, and other studio magic, he can sound a lot better in studio. But I think he has lost much of his gift.