It's blended with a Group III base stock and the "6" oxidation number indicates that it has about enough ester in it for seal sweller, just like any other HM oil that's blended with Group III mainly. I doubt Valvoline would fork over money for ANs, as they've never done so historically for their mainstream products.
PBR is a niche product, expensive, and hard to get a hold of. R&P is no PBR, that's for sure. I say it's a new way of marketing a High Mileage oil. They probably came to the realization that calling a motor oil that's got a little more "kick" to it "High Mileage" isn't the best idea. I mean, these folks have a High Mileage oil for vehicles with over 150K miles. What's different about that one?
@Foxtrot08 called it a while back: It's Valvoline marketing at its finest.
I wonder if they use Glycol Ethers as seal swellers, or something else. Again, an FTIR would point out these individual components, including ANs.