Pretty sure that's always been the case.
https://www.alaskaair.com/content/mi...y-wallet-terms- My wallet credits may be redeemed at alaskaair.com for air travel on flights operated by Alaska Airlines flights 1-999, 1000-1999, 2000-2999, and 3300-3499.
- My wallet credits may be redeemed for new ticket purchases only and cannot be applied toward service fees, or as additional fare for exchanged or partially used tickets.
- My wallet credits may be applied to transportation sales tax, security fees, and Passenger Facility Charges.