I'm flying next Sunday night on a fare booked more than 10 days in advance that booked as an MUP into A for the outbound. It was the cheapest option available so it passes muster with my company's cheapest fare policy. And on my last trip both directions were booked as MUPs into A.

I think DL has definitely been selling more revenue F tickets, especially when their option is as cheap or cheaper than the competition's coach fares.