I have been on several flights with pre order meals and our meals came with a sticky on them that showed our name, seat number AND PNR along with some other stuff. In every occasion there was enough for everyone on board.

I do not doubt for a second that there will be a flight or many flights that only got pre orders loaded (I thought about this quite a bit before pre ordering) On several of those flights we pre ordered stuff that wasn't actually on the menu for that flight. I am not saying it is right, just more United "Good Leads the way" They try and do something good and screw it up royally.