I had one of these about 5 years ago on a United return DTW-ORD-MSP. A friend and I had flown out that morning (I want to say on a Tuesday) to attend the North American International Auto Show, which was awesome. On the way back, which I was believe the last flight of the night ORD-MSP, there was maybe 15 of us total. I remember, after we were all boarded, someone raised their hand and asked the FA "Excuse me. Do you mind if we..." and before she could finish the FA said "Sit wherever you'd like." I took this upon myself to join the 1 member of FC, to which the FA had no issue. I didn't partake in any of the F amenities, which were happily provided, but it was at least a more comfortable seat. Having a drink or taking snacks just seemed wrong, even though I was there with permission.