Thank you very much for your feedback and concern we appreciate that 🙂
As far as I know, @import has been used only in editor-styles.css file. And this file is not used anywhere in the front of the website which impact the loading of the site. editory-style.css file is used in the editor in the backend to show the visuals on the editor as close as front end. You can read about it about it here : http://codex.wordpress.org/Editor_Style
And there are times where you’ve chose between usability vs code standard and we’ve chosen usability here as it’s not impacting the loading time of the site for the users who are visiting the site.
If you’ve found imports in other places do let us know we’re happy to fix them.