It doesn't appear to be a "game", but rather a function of the demand for various segments on the flight. I found a 12.5K routing of the type you wanted on Christmas.
Flight operated by Horizon Air Arcata/Eureka (ACV)
12:10 pm Fri, Dec 25 Seattle (SEA)
2:59 pm Fri, Dec 25
QX2308 One stop/plane change
Duration: 2 hr 49 min
Flight operated by Alaska Airlines Seattle (SEA)
6:55 pm Fri, Dec 25 Fairbanks (FAI)
9:53 pm Fri, Dec 25 AS129
AS129 Nonstop
Yes, AS did inflate mileage requirements DL-style, which is unfortunate. But it seems what you're encountering is no saver availability on either ACV-SEA, or SEA-FAI, not a conspiracy to make you overnight in SEA.