Chrome / Chromium is webkit-based as well. But there are minor differences and many people just do not bother to test their sites under desktop Safari, assuming the majority of Mac users switched to Chrome or Firefox. Though I agree, Firefox is much better in terms of privacy, Safari being the second, but there are privacy-enhancing extensions for Chromium that make it not that bad.
Anyway, Chrome works, Firefox works and Safari is constantly giving me issues with Evernote 😕