I don't see why software has to be created specifically for a "pro" line of iPads, instead of letting all iOS devices access those features directly.
File management, split displays and even support for USB-C are something that could benefit both iPhones and iPads equal, not just a larger iPad. If you want developers to support said feature, it should be something accessible on as many devices as possible to make it worth their while, rather than being restricted to what is probably a niche market at best.
Likewise, software like final cut pro or photoshop for iOS is not something you really need a dedicated file directory or split-screen capabilities for anyways. Assuming all specs equal, I don't see why an app designed to run on an "iPad pro" should run on an iPad air.
I just don't see the merits of your argument here.