I think the Government saw the writing on the wall and skipped the request for an EnBanc Panel hearing and went straight to the SCOTUS since the DC Circuit ruled differently on the issue and there now exits a split amongst the Circuits.
Also, it's kind of important for the SCOTUS to take it as there is some uncertainty as to whether whatever the CFPB does going forward could eventually be overturned, as well as past agency decisions, by the courts in more than just the 5th Circuit (i.e., Texas, Louisiana, and Mississippi).
I'm pretty sure that's right.