Finally heard back from Hertz. Got the usual "sorry we didn't live up to our standards, etc". The are crediting back the upgrade fee of $15, plus some taxes.
Part of the problem is Tulsa is a small market. Premium is no longer reservable. Luxury is usually sold out. I've seen Mustangs and Cameros, but they are not reservable. National is the same way. Can only book up to a full size then SUV's and vans. Since its not an Aisle location, you likely get an Impala.