The squaretrade (who does 3rd party extended warranties) report was an analysis of several years of data and some 30,000 warranty claims (if you're talking about the same one I read). So the "most reliable brand" was assessed under those constraints. You can make whatever conclusions you want w/r/to that report but I don't think that under those constraints you can establish one brand's reliability over another.
In my experience it's not brands that demonstrate reliability/unreliability, it's individual model lines. For example my Dell 5150 and my Lenovo T61P were both steaming piles of pooh when it came to hardware reliability, and both of those models have had a considerable number of hardware complaints about them. Also a...