I believe it was the oral argument of LendingTree v. Zillow in which the patent owner mentioned “secondary indicia of patent eligibility.” Because the Supreme Court has conflated patent eligibility with obviousness in its Bilski-Mayo-Alice line of cases, I suppose it is a natural evolution for the patent bar to begin to rely on traditional 103 arguments to establish patent eligibility.
The argument would be that if the elements of a claim as an ordered combination recite something that has achieved, for example, commercial success, then the claimed invention must not have been well-understood, routine, and conventional, as of the date of its invention. Therefore, the nature of the claim has been transformed into a patent eligible application.