With an iPhone you've got a shiny device that just works and doesn't come with shit installed and that you cannot tinker with.
With an Android you've got a shiny device that many times comes with shit installed and that you cannot tinker with (depending on the manufacturer).
The difference: you can build your own unlocked Android device, and because of competition there will be phone manufacturers that will do just that.
Windows PCs aren't locked, and this came to be mostly due to harsh competition, or am I missing something? Don't you think the likes of Compaq/HP would've rather sold locked devices akin to gaming consoles (also popular at that time)?
You're saying it is "theoretical openness"; I'm saying the market is too young for Android's openness to unravel.