You can't compare that. I'm pretty sure that some moderators were invited with even a lower percentage. As stated in the rules, moderators are allowed to interpret rules as they wish (to some degree).
He might have been wrong less than 5% of the reports if someone else was handling his reports. I assume that he made mistakes when he joined the forums, as did I. I'm also now at 95%, it is just really hard to get it much higher.

I think that theymos has stated somewhere that 90% (or even less?) was enough.

Your success rate doesn't actually matter all that much. If you're above 60%, we'll teach you the rest once you become a mod. As long as you can maintain that, quantity of reports is much more important than quality. Specifically, we're looking for people who report things during time periods where the reports aren't immediately acted on, because that indicates a need for additional moderators for that time block. People who report things during those time are far more likely to be chosen, and you're more likely to report during those times if you report more in general.