I can recall a year or so ago Mr. Chicken offering to "upgrade" me on a flight for which I was at the time waitlisted. As my upgrade had still not cleared, I was needless to say not pleased to see him trying to sell away paid upgrades.

I believe that sort of situation is what prompted the concerns originally, that UA would both hold back on upgrade inventory and that they'd potentially try selling it off for $$ before processing instrument-based u/g's that had been waitlisted.

Maybe UA has worked some of the bugs out of the system? I haven't noticed this recently, though I do rarely waitlist anyway.