Of course the FO is less experienced. Point accepted.
However there is a world of difference between the qualified FO and a plumber's apprentice. It's a very poor choice of comparison indeed.
Bunk time is counted by CAA mandate. Like it or not. It's also irrelevant to the discussion of the principle of forced draft. Of course I could ask if the captain is on rest and something goes wrong, is he no longer responsible?....
However in an attempt not to get sidetracked....
The point is, irrespective of arguments about how many hours have been worked and what they were doing at the time, is it accpetable to be called and told you MUST do overtime, irrespective of any family commitments/arrangements etc. I have an annual event I attend in mid summer for one weekend. This year, after failing to get any useful leave, I succeeded in getting the weekend off through bidding. I have waited all year for this chance to meet up with old friends and bought tickets to travel to the appointed place. Do you think I will accept a call from BA anytime in the preceding week or so?