> GAO is a Congressional agency, it does not fall under the Executive
Ah ah ah, you're describing how things were before Trump v. Slaughter, when the Supreme Court justices ruled that Republican Presidents are allowed to fire the heads of non-executive agencies so long as they are not the Federal Reserve.
[dead]
You must have missed the Chevron doctrine case where the supreme court took much of the ability for Congress to give away their power to the executive in the guise of creating agencies.