Yes they will do this, Second dinner is often not full and they can accommodate it.
In Alaska as well as Med and Baltic, we have been offered.
(1) To go late to the Main dinner, ie up to 30 mins post it starting.
(2) An offer of switching to Late.
Often on late port days the buffet is open Beach blanket in Alaska,
Recently we were in St Petersburg, Russia we knew we would be back late as the ship docked overnight. Our planned arrival time was 8.45 that's 15 mins after Late had opened up.
The head server said he would accommodate a switch from Main to Late and us turning up 15 mins late.
We in the end over shot our planned ETA so we went to the buffet, this would work for Alaska as well.
