but if congress explicitly states that agency xyz will update specific numbers wouldn't that be pretty solid? As far as I can tell, this is just about leaving it up to the courts when things are ambiguous, which is kind of the point of courts.
Sure, but "EPA to determine methodology, including statistical parameters" is still ambiguous.
What's the process for determining the methodology? Would another process have been better? Does the plaintiff's proposed approach for methodological determination also conform to this law?
In this case, "how to go about determining methodology" is left ambiguous, and is now the province of the courts, not the EPA.