If that's the case, note that the seats in F are the same as in J, except that the J seats are 2-2 and therefore the window seats do not have direct aisle access. I've flown in F on this bird but not J.
In F you will get regular F domestic service, and in MCE (including rows 6-10) you will get regular MCE service, whatever those are at the time.
So if you get a "First" or "Business" confirmation and are in rows 1-5, that's what you'll get. If you get an "Economy" confirmation but are in rows 6-10, you will get a lie-flat seat.