I think the issue is getting back to the OP - how they sell the F cabin. UA these days is mostly 1K, 1P etc on UDUs in the F cabin, and paid F. I have not seen much upsell passengers at least based on the lack of cheap upsell tickets on UA and the long list of people waiting for UDUs. Also the conversation around me tends to be suggest there are alot of FFs on upgrades of paid F.
If you read the UDU stats you wil see 1K is about 83% and I believe 1P is over 50% at least for those reporting from flyertalk. They start UDUs for 1Ks at 100 hours out. We are all kind of waiting to see what happens after the merger.