There's nothing particularly insane about not breaking the APIs with every single release like OS X does with user-facing stuff or Linux does with kernel-facing stuff.
In fact, you have to go the extra mile to break stuff.
You'd be surprised, because a lot of Windows software developers do unholy things like plugging into undocumented APIs or modifying parts of the OS that should not be modified.
Previous leaks of Windows source have indicated Microsoft ends up putting in a lot of workarounds to give specific third party apps old functionality just because some app is popular and badly written and a fix for something else broke it.
Can you please give an example of something that is used frequently and that is as backwards compatible as Windows. Android is not from my experience(having to be often be recompiled for newer version.)
Previous leaks of Windows source have indicated Microsoft ends up putting in a lot of workarounds to give specific third party apps old functionality just because some app is popular and badly written and a fix for something else broke it.