I just tested it out for my return one way. I saved $1 by booking it at airport.

I added it in my profile and it recognizes my status so I can select seats, including stretch, and I can get free carry on and free checked bag. I could just click and get "The Perks.". As you can see in the screenshot, you don't get "The Works" like you do when you book it directly on the website. So technically this means I can't cancel flight for free as I don't have "The Works" on this ticket I bought at airport. I suspect this is for the reason I mentioned as "The works" being only available for "purchase" at booking. I put it in quotes as we technically "purchase" it for free by clicking on it as a 100k.

Now, I wonder if you could still call in and argue that you should get free cancellation as a 100k because they don't have a disclaimer saying you have to book it online and not save money at airport and should have the full "Works" as a 100k.