Correct me if I'm wrong, but this feels like a long-winded way of saying: if an adversary could control a significant portion of relays without being found out and for a not-insignificant period of time, it could defeat Tor.
Is it correct? Probably.
Does it justify the "Not secure at all" indictment? No.
Is it correct? Probably. Does it justify the "Not secure at all" indictment? No.