<< Mnuchin... Fox... Sunday appearance >>
I believe he is in Biarritz, France with Trump for the G-7 leadership conference. Unless he is returning, today, I seriously doubt he will be talking about a narrow, domestic agenda item like GSEs from that venue. His schedule is posted on the FSOC website, weekly.
The appearance definitely is scheduled for Sunday @ 9 AM and is on Fox News, not Fox Business.