I think he fully understands the the PCs potential--he even remarks on that in the quote.
He's just confirming what most have known for years: it's hard developing on for a PC: API constraints, endless permutations of hardware configs, unknown myriad of other softwware running concurrently: it's much easier to code for a closed ecosystem--you know what hardware and software will be running. Always. Its the same thing that makes iOS development so enticing to a programmer.
Honestly? I probably wouldn't have a problem with it if MS added a mouse, browser, and a keyboard. But that will never happen.
While I'm disappointed he's taking this position, I get it.