Late post, but have had tons of success recently! All flights were booked in mid-January.

MVP Gold
AS 539, 737 MAX 9
SAN-SEA
3.26.21
Upgraded to FC at check-in, Fare class R

AS 442, 737-900
SEA-ATL
3.26.21
Upgraded to FC at check-in, fare class R

AS 443, 737-900
ATL-SEA
4.5.21
Upgraded to FC at check-in, fare class O

AS22, 737-900
SEA-ORD
4.5.21
No upgrade, manually selected Premium Class at T-7 from Expertflyer alert. 5th on waitlist and only 1 FC seat available - not particularly surprised considering day after Easter and midday.