I don't know the answer to that, but when I used miles to upgrade to first on domestic, my fare said F for about a month, then last week it changed to economy R (flight is the end of this month). I called the elite line and they said I was still in first.

That doesn't really answer your question, but thought maybe someone understands what's going on. My upgrades have always said First (F)..this is the first time it has read economy (R). But my seats still say 1F.