Did you look at the COC when you agreed to the terms? Rules 4 and 9 make it clear that if WN cancels the flight, it may either refund the ticket to your original form of payment or issue a travel credit, at its option. It is the only US carrier which does it. But, you agreed to the term.
Whether WN does refund the ticket is an open question as you have not even made a request yet. Historically it has.
I would ask for a refund and not cite to documents you have not read. Just ask for a refund because the flight is cancelled. If there is a problem, it is an open question as to whether the provision will stand up, but you are nowhere near that yet.