well, it is unbelievable because in order to work 80hrs a week (i.e. around 14 hrs a day) you need a very strong mental and physical health. To have strong health you need regular meals, sports etc, i.e. time to do it. I dont believe but if it is true, it wont last long. He might end up in hospital, in the best case in a normal one, in the worst- in mental health care institution.
My supervisor says that 5 hours of a good work a day, 6 days a week is completely enought to finish your PhD in decent time.