For F, it depends if the A class totally disappears or if it is not bookable for "normal price" awards. If one cannot book normal F award, it could mean that F can be flown with paid tickets or as upgrade from J, which is not that bad: regular J passengers, that bring revenues, have more chances to use their miles for upgrade. If however the A bucket totally disappears, it means that there is no chance to fly F reasonable ( = without paying for F).