A friend of mine was the 2nd highest placing individual hunter. He was using an Explorer, and scored 6 period coins (colonial copper, half cents, etc...), and dozens of period items. The way he explained it was that the overall brand score was sort of meaningless, for several reasons:
1) there are so many applicants to get on the teams, that the organizers have to use a lottery, to see who actually gets on the teams for the brands. So often time, you have a newbie rookie using, let's say, a Minelab for instance, who might find practically nothing. That brings down, in this example, the Minelab score.
2) The Nautlius is a niche machine, almost exclusively used by hardcore CW/colonial hunters. Ie.:, it's not the type machine newbies/rookies gravitate towards. So basically, the guys that get on that team, are by their very nature, hardcore experienced users, who will of course outscore the more cross-sectioned other-brand teams. That's not to say that Nautilus isn't a good machine/brand, but just that that team is more likely to be aces to begin with.