Like seven standard deviations better than their competitors. Maybe they're just that good, but normally when something is that far out of the norm it invites suspicion.
It is right and proper to doubt the results as published in that new book.
It's the tone though that surprises me on what I expect is a more technically oriented site. I'm now half expecting an accusation that Renaissance uses witchcraft, or alien technology from the History Channel.
It's not a fair comparison to say they just "did the math" when there are thousands of other, highly qualified, highly intelligent people trying to "do the math" at the same time, all the time, yet RenTech has managed to always come out ahead and not just barely, but massively ahead.
I don't believe RenTech is doing anything illegal. I think they have a extremely significant edge that they've managed to maintain for a significant period of time and that should be suspicious to anyone who participates in the market.