It certainly has a lot of besseae influence in the breeding, but the flowers are just under 4 inches wide. I think it is too large to be straight besseae, and my gut feeling is that it will be even larger on subsequent bloomings.
Cahaba Glow = Sunset Glow x besseae
Sunset Glow = Eric Young x MDC
Eric Young = besseae x longifolium
MDC = besseae x sargentianum