It tells you nothing about their self esteem, it's about offering products people want to buy. Does selling Microsoft Office for OS X show a lack of esteem? (Hint: the basic Office programs appeared first on the Mac.)
In any case, Microsoft already launched a Universal Bluetooth Keyboard (works with Windows, Android, iOS) last year. It would be a surprise if they went backwards from that.
They guy who is marketing this keyboard is responsible for selling keyboards, so he lists them in the order of likelihood that the reader owns one. Speaking exactly, only 71 people on Earth actually have Windows tablets, so mentioning them first would only serve to make the author seem like a corporate toolbag of the highest order.
