A few months back I wanted to change a four-passenger BER-IAD reservation from one day in July to a different day. We were traveling on a W fare. When I looked at flight availability beforehand in expertflyer, and when I hit 'change flights' in the United web app, the availability shown from both sources showed that the flight was "Y9 H9 ... V5 W3".

Despite flight being V5 W3, the change-flights link offered to let me change my 4-passenger trip into W fare class. The change was completed successfully and we ended up with a 4-pax reservation in W. The flight was W0 afterwards.

I wasn't quite sure what was going on here, but it felt like United inventory was stretching a little and offering me the cheaper fare class on a multi-passenger itinerary. Without actually changing anything about the way multi-passenger airline records universally work, I still got a nice deal from United offering me a little extra flexibility. No idea how that happened but I was grateful. I wonder whether this was a real-life example of creatively implementing the kind of flexibility txp is wondering about in this thread.