Familiar. If you've read any of the literature on snapshot isolation or isolation levels in general (Berenson, Bernstein, Gray, Melton, O'Neil, O'Neil, Adya, Liskov, Fekete, Cerone, Bailis, Alvisi, Clement, Crooks, Pu...) you would probably not expect to see SI treated as stronger than RR. The paper which first defined SI says it's not. Heck, Jim Melton, who wrote that part of the ANSI spec, is a co-author on that paper, which goes on to say the strict interpretation is incorrect and not what ANSI intended!