They may care about the browser, but I fear they care about regaining market share more than anything else. They had a firm lead for a long time, but more and more I see sites making support for non-IE browsers a top priority and the IE market share is shrinking.
If Microsoft uses tests like these to try to divide the browser market by essentially defining its own spec, I think it will be bad for the internet at large.
To be fair, these tests were submitted, and apparently developed with the W3C. They aren't MS-only tests. Merely tests that needed to be developed anyways. At least, that's what I see. Yes, these are tests where MS succeeds. That doesn't mean they are less worthy. Rather, they are just more cases that the W3C felt needed to be tested.
MS is a big beast, and "market share" means different things to different parts of MS. The developer tools division, which makes, among other things, ASP.NET server-side environment for serving web pages, cares increasingly about working on any browser. And this is a good thing.
If you want to know what the IE9 team thinks about HTML 5 and cross-browser issues, try some of these:
If Microsoft uses tests like these to try to divide the browser market by essentially defining its own spec, I think it will be bad for the internet at large.