For a web developer 93/100 is more than enough, such a (high) score is well suited to do everything you'd expect from a modern browser. The need to hit 100% is overrated, if you're a web developer you know what I mean.
Firefox takes the approach of "what really matters" to web developers and users and that is not only passing the acid 3 test but also "next-generation" (HTML5) features like web workers (threads), native video, animated SVGs, Canvas and other stuff that other browser(s) that hit 100/100 aren't yet able to do for now, but which is much more welcome than the remaining 7% of the acid test.