I saw today at the end of this thread:

https://www.flyertalk.com/forum/alas...need-help.html

that Alaska Airline miles no longer expire, and it provided a link to the section of the terms that state that, so I updated the Wiki above to move Alaska Airlines to the Never Expire section with that link.

Would not fully agree with that. AS ffp needs activity to keep alive. Many other ffp's have the same activity rule, with a time limit. Often 18, 24 or 36 months.
For this thread "do not expire" means do not expire even when no activity. Like with UA

https://www.flyertalk.com/forum/36348691-post15.html

Just about every program that has no miles/points expiration has some policy for needing to keep the account alive. That's not unique to Alaska.

And the second quote you included says: "Mileage Plan miles do not have an expiration date and may remain in an active account indefinitely".

So, Alaska no longer needs activity to keep the miles alive, just some unspecified amount of activity to keep the account alive.

And btw, not only the airlines and hotels listed under Never Expire have this kind of no-expiration policy. Some programs, like Marriott for example, have a no-expiration policy just for members with certain level(s) of elite status. But again, you need occasional account activity, it's just not specified how often that has to be, to keep that account alive. But it's certainly activity that's less often than the expiration period for those people who don't qualify for the no-expiration policy.