Originally Posted by brunos

But I also remember discussing with some purser, the situation where there were fewer FAs onboard coz the flight had very light load. I was told that the agreement on number of FAs precisely described which cabin or sub-cabin were closed. I have seen case when the J min-cabin was closed (I don't remember the ac). That makes sense in terms of service. She said that this was detailed in their agreement (there is a technical word for that agreement).
I am not privy to the agreement in F, but I would suspect that the 5 seats open should be nearest to the galley for service purposes, as it is on the 5P maps. So there are two possible explanations.

And I am sure that there will be AF crews which will strictly enforce the agreement, serving meals only in the seats near the galley and letting you move only for sleeping. .