I was basing my reply more on an already implemented design of windows 8 for desktop and tablet. The tablet version will not run the applications from the desktop version, thus making the only thing similar between the 2, the metro UI crap.
ubuntu is essentially doing the same thing.
You may get the unity UI but the similarity ends there, you wont be installing the desktop version of firefox, chrome, open office, your various coding and compiling tools, gimp, various other tools, unless they make a ARM version.
Because of this, a user is not provided with the desktop experience on their mobile device, because the applications will not be the same on both devices, meaning you cant work on something like a file in gimp then continue to work on it with your mobile device, then dock it with your desktop system and sync the files over and finish working on it on your desktop PC.