Datapoint:

UA1619 on 3 May - LAX-SFO.
R/RN = 9.
Seat map shows 17 of 24 seats unassigned (7 Booked in F - 5 upgrades which matches UA Flight Status)
At 96 hour window, 2 * 1K do not clear on a K fare.
Reservation is updated to Complimentary Premier Upgrade Requested.
"TOD" - offered on reservation page $239.