Mostly Agree, but...
Microsoft aptly proved with Windows 8 that a unified ecosystem - let alone an interface - for a Phone, Tablet, and a desktop is not easy to get right.
Their Windows 10 idea of the same Dev tools and binaries that adapt to the environment they're running on (Continuum) seems a better approach.
I think Apple's way of doing it (Write the best desktop software, and the best mobile software you can) is a better idea still: Although the gap between what we use a tablet and what we use a computer for is closing all the time, they're sufficiently different still to make a unified system a little awkward - I can see them merging some point waaaay down the line, but here in 2015, it seems a lot of pain for not much gain.
What may be beneficial (And correct me if it's already there and I missed it) is an end-user ready Emulation or shimmy to allow you to iOS Apps on OSX - yes, most people won't have a touchscreen, but I can think of quite a few apps and games where the iOS Version would be a great fit for the desktop environment, and it a nice way to get more value out of your apps, and possibly a few easy sales for the developers.