On my ICN-SFO flight last week, a mother and two kids had seats EFH in C, with dad in the back. For the meal service, dad moves up to C while mom goes to the back. After a while mom is back in C, dad is again in the back. They made at least one more swap so dad could work on his laptop. Maybe even another - I stopped paying attention to it. I napped through breakfast, so I don't know who got that.
With full knowledge of the FA's.
So it does happen.