Makes no sense. The NSC seems to have leaked the story deliberately, presumably to send a message to Moscow: If you get involved in the next election, your lights are going out.
That's an obvious, long-overdue message.
Having the capacity to do this means nothing unless we make it known that we have the capacity and make it clear that we will use if if provoked in specific ways. Leaking to the NYT is a form of signalling--
Making it clear that we can and will retaliate if provoked is necessary to protect a vital national interest--the security of our elections.
So his objection can't be to the leaking, which seems to be authorized and strategic.
Or is he denying that we have this capacity, and if so, why? If we *aren't* doing this, he needs to fire everyone in our national security establishment.