FWIW, they use PayPal extensively. They do have a very small staff, they aren't Redweek, and you will see the same names responding to their email queue.
As you know, it's not a hotel reservation, so the owner may not have another alternative, i.e., it could easily be a fixed week and no way to rebook another week for you. Technically the owner controls the reservation, subject to the contract, and apparently the owner is enforcing the contract.
If the resort is closed, then you get a full refund per the contract.
August is still a ways out, but I would expect resorts to start opening by then, to some extent. One of the Facebook pages noted that Kaanapali Beach Hotel is planning for a July 1st opening. Life there will be different going forward, and you'll be on the leading edge, but you will be on Maui. ;-)
I expect the bigger risk is your flight being cancelled or rerouted via HNL trying to get to Maui as all direct flights are being suspended.