Yeah he probably is. Sarno wrote a whole range of books, primarily about back pain (https://www.saxo.com/dk/healing-back-pain_john-e-sarno_paper...), but also dealing with RSI. If you read up on it, a great deal of people have said it has helped them with their RSI.
Anecdotally it's done nothing for my RSI, but it has helped me deal with a 7+ year "chronic" upper back pain, though it did take a bit of time to swallow the concept at first.
Anecdotally it's done nothing for my RSI, but it has helped me deal with a 7+ year "chronic" upper back pain, though it did take a bit of time to swallow the concept at first.