Had a quasi or "fake" Op-up yesterday from ICN-FRA (on a Z fare) to an F seat (seat only!). On boarding, boarding pass beeped, and was moved to a single F window seat (old F A346) and told that it would be J service only. Apparently, no F seats were sold, and J may have been oversold, so they seated HONs/SENs in the F cabin. Kind of funny. but the very nice crew really made sure that we only got J service too, LOL! - they only gave out blankets, and even though the mattress padding was available in the drawer at each seat, they pretended it wasn't there
....And they didn't bother putting up the partition between rows 1 and 2, so the person in row 1 when fully reclined had his head a few centimeters away from my feet....
And of course, the curtain between F/J was left open during flight, we got the J amenity kit, the J meal service, etc.