A week or so ago on AS1193 SJC-SEA, just before 72 hours out, there were only 2 occupied F seats.
At c.71 hours myself and all other MVPGs were upgraded (nobody showed on the waitlist afterwards, but the available F seats reduced.
The flight ended up going out with at least 4 empty F seats, including the one next to mine with nobody in the waitlist. All MVPs and above cleared easily.
It is a 6:15am flight so not the most popular option, but it does go to SEA for lots of connections.
The eligibility for upgrades even at the lowest levels of elite is a real perk IMO.