Originally Posted by
fumje
As far as I am aware, op-ups are processed as simply changing the seat to the "wrong" cabin, in the same way, for example, that downgrades after CPU leave you in PZ/PN but put assign you a seat in Y. The flight will have credited as Y or O or whichever. So I'm not too surprised that the IT "correctly" denies access, since it's looking at the cabin rather than the seat, although admittedly I also would have hoped to get access with op-up.
This also messes with the upgrade list display, as a I learned last weekend. I was standing by for seats on an earlier IAH-DFW flight after mine was delayed 5 hours. There were 5 seats available in F, but nothing in back. It turned out there were sufficient numerous "no shows" to accommodate all revenue standbys (and some of the non-revs) but they op-upped 5 passengers without seat assignments first before unseating the no shows at T-15. The app continued to show 7/12 in United First and was listed as "available" (though all the seats were by then taken), which is how things remained for the duration of the flight -- but I cleared into the back died at the top of the upgrade list.