It is absolutely not grounded in any real statistics, it just averages a few things together that sound like they might be useful (record, opponents record, opponents opponents record). If you tried to present that as a legitimate model you would be laughed out of the room at every job I’ve ever had. Even a simple linear regression based would be more defensible. On your point about the strong conference schedule being what helps the SEC in the RPI rankings, you are exactly right and that’s why a more sophisticated model that can go beyond simple record comparison is needed. Any regression based analysis could better control for unequal scheduling. The NET in basketball is a good example of the NCAA realizing this and switching to a more robust, albeit still imperfect, metric. There is no excuse for this kind of antiquated “metric” having so much control over college softball/baseball. A volunteer graduate student could cook up something better in 30 minutes.