So, without knowing anything about how those scores are calculated, I'll point out that currently, desktop Safari (which is much less problematic than iOS Safari) is just behind Edge, a browser that isn't even at v1.0 yet.

Even the most literal "new Internet Explorer" -- Edge -- is a more standards-compliant browser than Safari, which has stagnated far behind every other competitor in the list.

So yeah, I don't mind saying it again: Safari is the new IE6.

Oh, and while you're on that page you linked, click over to "mobiles" and observe that even Blackberry scored higher than iOS (i.e. Safari, since you can't really get any other browser there).