bull****. Between applications that use the desktop as the default save and applications that clutter up your desktop with far too many icons (the program itself, the updater, the 3rd party crapware updater), most users desktops are a complete mess of crap.
100% fiction. 99.9% of all installs allow the option of creating a desktop icon and start menu entry. If users want the icon on the desktop, it's not convoluted. It's exactly what they want, and the desktop default is to align icons to grid.
The "Start" Page is populated by start menu items which 100% of users you're talking about (fictional users with a desktop full of folder shortcuts and whatnot in your mock up) create by default which makes a messy start page. Install any app and every little start menu shortcut from the main app to any shortcuts to help files, settings, uninstall shortcuts and the like overpopulate the Start Page.
I really don't care either way, but please stick to reality to make your points. Neither one of you know what most users desktops look like. But without a doubt, the Start Page is a mess if you install Win32 apps. You will be cleaning it up often and there is no way for it to elegantly handle lots of tiles. Perhaps in Windows 9.