Who has audited these numbers and what is your source specifically?
I‘m aware of Rentec for many years and also awed by the numbers but I‘ve always wondered where do people actually get them?
In particular: RenTech likes to keep a handle on this publicity for the purposes of courting extremely good talent from academia and industry. That's the only reason the Medallion returns are ever intentionally publicized. Anyone investing in RenTech's other funds knows full well they're not getting the alpha powering Medallion's returns.
Simons would probably have preferred to stay entirely under the radar, but the cat's out of the bag already and has been for decades. The most successful hedge funds (like the Princeton Alpha offshoots) don't court publicity because they don't need to pool risk with outside investors. They're not even hedge funds in the common sense of the term; they're proprietary trading firms run on employee and partner capital. Medallion can be thought of a prop shop within a hedge fund in that way.
Also, what Princeton Alpha offshoots? IIRC, Princeton Alpha was a PDT spinoff that closed due to poor performance. Maybe you mean Princeton/Newport offshoots?