"Well, here, you're just re-stating the default for all files, are you not (or am I missing something?)."

Actually you're missing something critical to the success of the test. I'm ensuring that the content of the CSS file is recognised as UTF-8, and not the encoding of the HTML file, which is the rule if the encoding of the CSS file is not specified. That would of course break the test. So a character encoding declaration for the CSS is absolutely needed.

(Btw, there is no .htaccess file for this support directory.)