Alaska no longer offers the policy I believe you are referring to, effective September 1, 2018 [1]. Their new policy, despite being advertised under the same name, only covers price drops within 24 hours of purchase, during which time you'd be able to cancel and rebook anyway. [2]

This is the kind of change that is not fun to learn the hard way.

[1] https://onemileatatime.com/alaska-airlines-price-guarantee-e... [2] https://www.alaskaair.com/content/deals/special-offers/price...