Tbh there is a good place in the world for "just a proprietary retroarch". Someone's gotta do the work to bind open source emulators to the proprietary sdks, and nintendo/sony/maybems? Don't let you do that in public code.

So an engine like this, if its basically just a case of dropping a rom in and customising a few menu screens, could help get a lot of things ported to modern systems if companies didn't want to put in the effort before.

They hype is really just to spread that word to other companies likely.