Yep, I see that one too booking into P and not A. The flight applicability for LAS/MIA appear to be the same as I posted above. You can buy an F or P fare although the P fare is a lot less but more restricted.

Just a guess, but maybe they are trying to distinguish inventory that is available for sale (P and F) vs miles upg/eVIPs/AONEx (A) and be able to offer a discounted First on selected routes.