GC I am sure that Pax do make some really entertaining pitches that staff can enjoy afterwards ... One should also point out to would be upgrader: Due to an error by a carrier, I had a letter of apology and a cabin upgrade on my next sector. At the time, I was doing a project in HKG and the client would only pay for me to go Y, so this was a valuable document.
Within the 12 month validity of the document, I was not on a flight with spare capacity to execute the upgrade.
I know that they did try and I did check out the fullness of the PE cabin. Such is life and airlines are going to suffer from this problem for many years to come.