Um, not exactly... F Seats are held for sale. Medallion upgrades come from a limited inventory (G/V fare buckets). If the F seats remain unsold, then those seats are available for upgrade requests at the time intervals listed. If there are still unsold F seats then the remaining seats are available for upgrade at the gate (the gate lottery) or even sale at the gate (if all Medallion requests are satisfied and there are still seats available).

Now, this does not negate the other comments by BamaVol. If upgrades have taken place, then those preferred seats have been vacated and may be available for your request.