MAybe it's because they chose a plane that has been mass produced by so many othher companies, that the market is literally saturated with the variant, not to mention that it's more expensive than the TF version, regardless if struts are included. Just a thought of why it could be.
I'm not really a P-51D guy, but if I were, I'd probably buy a cheaper version at 1/2 the price of the new H9 (regardless of it's new features)and bash it into something comperable.
But that'd only my opinion. I do think it's a beautiful plane, but a 120 size plane isn't much more. Perhaps I'd change my mind if I flew/ had one .