It's not unthinkable that they'd move the transponders for a secret mission, no?

Also Hersh's point about the NATO head being an asset in his late teens is definitely feasible, as that was exactly what the Norwegian government did at the time - https://en.wikipedia.org/wiki/Lund_Report

According to Hersh the bombs were planted during joint naval exercises. That's a time when lots of people would be surprised to see a ship sailing around with its transponders off.

Your link is about illegal electronic surveillance and contains nothing related to recruiting random Norwegian teenagers as agents in the hope that they would become General Secretaries of NATO 40 years later, and thus somehow (?) able to direct clandestine missions of the Norwegian Navy.

Let's turn it around: Is there something Hersh's source told him that was surprising and could be verified independently?