He just explained that he has no intention to dox himself plus with 31 years of experience he is one of the few in his field. Do you think you would be able to catch up and be able to stand your ground in this market with less than say 10 years? It wouldn't make sense and you probably wouldn't risk doing the change so even if he thought it made sense to send you an email, it would be for nothing. You can still get his advice and use it for the specialization you can get based on your current experience.