Not disagreeing with you at all but wasn’t his dad a season ticket holder? A lot of times sons follow dads in the support of a team.He was certainly not a big Boro fan up to the age of 16 i can say that as a fact. Did he become one after that point when he was at Leeds? Well it's possible but it would seem odd.
Not that it matters, in fact it's probably a hinderance for a manager.