This is part of why quality of practice is as important as quantity.
On the one hand you have people like me when I started learning guitar - messing around with no clear focus or plan or progression, getting minimal benefit from practice time.
On the other end of the spectrum you have people who push their physical limits without regard for the consequences. Being the kind of musician who practices 6 - 8 hours per day is like being a professional athlete who primarily uses the smallest, most delicate muscles and tendons. If you don't structure your workout intelligently, you'll end up with overuse injuries like the gentleman you interviewed. If he had more awareness of what could happen, there are a lot of things he could have done differently.
- Warming up thoroughly before practice
- Proper cooldowns, pre-hab exercises, massages, proper nutrition, etc
- Focusing on proper ergonomic technique
- Being aware of the early signs of overuse injuries so as to back off on intensity and/or quantity of physical practice
- Devoting practice time as needed to non-physical aspects of practice (ear training, music theory, reading music, transcribing, recording techniques, etc). This could be especially useful during periods when the body needs more recovery time.
- Seeking specialist medical advice and intervention before he reached the point of permanent injury
Then again, even if he did some of those things he still might have had problems. As I mentioned above, professional musicians at that level are essentially professional athletes of the small muscles. Professional athletes push themselves to their physical limits and sometimes have career ending injuries.