Yes I would consider Matt an expert on Google related SEO issues. Yes I would treat his answers as Google's offical response.
I don't think it matters who much of an expert you are talking to. You have to use good critical thinking skills and look at how what they are saying fits with what your experience has been on the issue. Then no matter what, test, test, and test again. This is an industry that changes continuously and you have to continually adapt your methods.
