This is an opening for Moody’s to gain a competitive advantage over S&P.

Moody’s can announce that whereas any issuer of it’s own currency can always make nominal payment on a timely basis,
ability to pay is absolute and beyond question for the US government.

Therefore, when reviewing the US government’s credit rating, only willingness to pay is a consideration.

And given the recent Congressional proceedings regarding the debt ceiling,
an entirely self imposed constraint,
Moody’s is putting the US on notice with regard to willingness to pay.