Both AA and UA have programs in place to reinstate expired miles, so Alaska would not be alone there. The difference is that AA/UA require some money or flight bookings in a fixed period to get the miles back, versus just reinstating the miles outright. Surprised Alaska makes it so easy. I looked around and can't find any prior threads addressing Alaska's policy in this area. Have they done something like AA/UA in the past, or do you just write the miles off forever if you miss the expiration date?

https://www.flyertalk.com/forum/amer...challenge.html
Reinstatement of Expired MileagePlus Miles [Consolidated]