I’m either having a blonde moment or I am a bit confused on how this works. As a Gold, if I search for award flights, checking the button for MVP Gold upgrade type, I see three different fare types: Main Cabin, First Upgrade and First Class. U is available (F is solid blue).

If I choose the First Upgrade fare, should I not be upgraded to F immediately as U is available? I just tried a booking and it did not automatically upgrade me to F. Or is this not an instant upgrade fare? How does one know?

I thought all awards were now comp upgrade eligible at my window and that choosing the First Upgrade fare would be like booking an instant upgrade revenue fare, which would get me into F immediately as long as U was available. Adding it to the cart does not help as it does not tell me what class it is booking into.