Just wanted to round this story off.
So it took a while for them to reply to my email asking for credit. I just sent in the outbound couple of boarding passes (technically just needed to send the first one but it was a stub so wanted to be safe).
Everything credited quite nicely! Managed to make it to MVP with this one trip which I'm very pleased about and earn myself >50k Alaska miles which is a very good return on spend.
So TLDR: it works!