Rosa arkansas Porter was based on a doubtful specimen allegedly collected in the Arkansas Valley, high in the Colorado Rockies.
Aside from that quibble, you make an important point. I suggest that R. setigera has not been given a fair chance because the hardier accessions have not been used. Feast started with seeds collected in Ohio. Pierce used plants that originated in the milder climate of Tennessee. Horvath lived in Ohio, so I'm guessing that he used local plants for his breeding. If anyone has tried plants from Michigan, New York or southern Canada, I would like to know about it.
There is a related issue that (I think) needs exploring. Somewhere in my notes I have a report of a European orchid that has a fairly wide distribution. Someone had three accessions, each from a different country, growing side by side. Despite experiencing identical conditions, the three specimens bloomed at different times. Would this be true for roses?
Rosa setigera reportedly ranges from southern Canada to northern Florida. If specimens were collected from several locations along the range, and grown together in some congenial middle-ground, would each plant have its own preferred bloom time?
In Kentucky I saw numerous examples of two-toned dogwoods produced by planting a pink specimen beside a larger white. This created a very attractive effect. I think a similarly attractive effect might be had by having two once-blooming roses of similar appearance but different bloom times trained together. For example, Horvath's 'Polaris' reportedly blooms for five to six weeks. If paired with a Setigera hybrid that began blooming later, one might have 2.5 to 3 months of bloom.