The general usage patterns of iOS were never developed with user testing at the core. Same for Android Holo. These designs were created directly from a designers intuition and have since been improved slightly with user feedback and testing. If you read up on publicly available information about the process though, it is clear that user testing was not the central issue.
Meanwhile whenever you read anything regarding Windows 8 or Unity design, the use of user testing was always core to the design process - often toted as the most important part. Just read this article and the main theme of their design discussion is on user testing.
Basically, I think this area needs more research rather than an off the cuff "you need to test them on actual users in order to benchmark what works and what doesn't". Sounds correct, but has anybody actually tested that? Often your test users don't see the big picture and don't really know themselves what they want. They're just answering 'big blocks were easier to click on'. That doesn't mean you must use big blocks - you need to consider the interface and usage as a whole, not simple data points from testing and consider your design done...
If they take 10 minutes to figure out one interface and 10 seconds to figure out another one for example it's quite obvious which one is more intuitive.