As the statute unambiguously refers to regional inconsistencies from the delegation of the Administrator's powers, and moreover, implementing judicially-created inconsistencies is a reasonable resolution of the (un)ambiguity, no error in agency's inconsistent remedies implemented in response to bifurcated judicial review.
https://www.cadc.uscourts.gov/internet/opinions.nsf/C030B5F7DB87A8DB852582A600521E70/$file/16-1344-1734993.pdf
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.