I think that is fair enough if visiting friends for dinner. But when paying for a flight which has "dine anytime" as a core product feature it is really down to the crew to manage this. I think it is a bit patronising otherwise. If the crew said "we really cannot accommodate that tonight because one of us has a limp" would you not complain that the service standards were not met?

I am pretty sure it is more convenient for the crew for everyone to eat at the same time (that is why it is rare for crew to make passengers aware of the dine anytime option) which is presumably why many F passengers order to eat straight away as if they were in J.