Performance optimizations are all about trade-offs, and what might be a good trade-off for Microsoft's own hardware could be a bad trade-off for 95% of the other hardware on the market.
In theory, Microsoft could ship a second set of bits for their own hardware. But now you start to have nightmares about the antitrust lawsuits in the 90s. Why is Microsoft keeping a secret faster Windows that only it gets to use? That's the headline anyway.
The only way for Microsoft to achieve the kind of vertical integration that Apple has would be if it was willing to destroy its existing OEM partnerships. And risk a lawsuit from the DOJ. And this is a crazy strategy, because Apple has all the experience manufacturing hardware, and Microsoft has very little.