I'd bet this is simply a case of the right hand not knowing what the left hand is doing. I had no idea Microsoft were sponsoring Mercurial--even that seems odd, spending money on an open source competitor to a product they also make.
From a bigger-picture strategic sense, the Developer Division at Microsoft is concerned about making Microsoft a good platform for developers. Fundamentally, if developers want to use Mercurial on Windows or Git on Windows or TFS on Windows, we're happy. And - increasingly - we'll donate money or even developer time to help make this a good experience.