Not sure it's a glitch or change in policy but my point is that if long sell doesn't help for classes which show up on M&M and not on partners then it should not help here either. Unless you had success...
I could long sell LX I class in Amadeus. Maybe it is a good idea to try long selling it via UA/AC...
Would they only know how to long sell. And those people usually don't like the idea that I teach them how to work around....... Though I once had a DL agent who tried protecting me on UA but the flight was not showing in her system so I told her to try bringing in the flights via Amadeus, so she told me she never used Amadeus so I told her "I'll walk you through" and she accepted!