Seems like AK is changing the claim form slightly. There is no need to submit lengthy explanation, presumably they would be able to check your booking and whether you actually boarded the plane or not.
I made a claim on the 16/12 for no show to claim back the airport tax. Got a reply today but not much information is provided i.e. booking number as I have another claim in progress. Also, not sure of their intend when they ask for my user name. Thought my email will be good enough since it's unique? I did provide my membership # when submitting my earlier claim.
On another note, I had a no show for a QR flight in Oct so I wrote in to inquire about the airport tax. Settle within 2 weeks refunded back to my credit card used for the initial booking.