What I mean is that the CSS should be minified to remove _any_ extraneous rules, and should be done automatically, just as it's done with most compiled binaries

What I mean is that the CSS should be minified to remove _any_ extraneous rules, and should be done automatically, just as it's done with most compiled binaries. If you're using those font styles later on, but still using the same stylesheet, that's obviously alright, the performance-testing tool would need to be updated in order to spider through all the pages to verify where each one is being used.