Trump is actually being modest in his claims of the presidential power to declassify by fiat, anywhere, anytime.
A president also can, unilaterally and at any time, even after the fact, change the official results of pennant and World Series games. Trump is an extraordinarily modest and generous person, so he has not so far made use of this power that all presidents have, and have forever after, but that all changes tomorrow. Trump will announce that all those bookies who made piles of his cash over the years by obviously fixing all those pennant and World Series games after they took his bets, are going to be legally required to hand back their ill-gotten gains. The sums involved exceed the annual GDP of many nations.