“Wouldn't the SCOTUS be reluctant of invalidating Dodd Frank (or Hera?) as over a decade of CFPB (or FHFA?) agency actions could in theory be invalidated?”
I would assume so. But they still have a job to do, and they can manage that reluctance in different ways.
One way is to simply not hear the CFPB request for Writ of Certiorari, I.e., wait for a different federal circuit to decide on a contrary but workable remedy precedent.
Another way is to decide the CFPB request on the shadow docket, though I think that option makes less sense because of the novel nature of the claim.