The (linked) Aandtech article on battery life pretty much answers its own question.
Surface pro and surface pro 2 completely destroy everything else in the benchmark ratings. It means haswell doesn't manage lower power scenarios nearly as well as ARM, but Intel never has.
For a comparison to iOS they'd need to well, actually have on on their chart. I can certainly see the argument that Windows is worse at power management than other OS's on the same hardware - but without hard numbers in a chart that's a tough case to make, since you're comparing different review sites to each other. Comparing different hardware is missing out on a lot - for most computing needs they're benchmarking Haswell is massive overkill - which might just be it, it literally cannot slow itself down enough (with either MS or intel drivers being the culprit) to save even more power.
Or windows is doing background stuff that other OS's aren't. Whether those provide any value to justify reduced battery life or not is debatable, but the answer seems to be 'probably not'.
It still isn't 'microsofts hardware', it's hardware from some 3rd party vendor they soldered together in a case and put their own sticker on it. Yes, it's up to MS to try and ride the cases of Intel and whomever is supplying their displays and SSD's to find ways to save power, but it's ultimately up to the 3rd party guys (who also sell parts to the rest of us) to actually make the drivers for their hardware.