Good summary.
The genesis was back in the 80s... it was Gary Ward's idea, IIRC, to generate more excitement in for college baseball in the state. Back then, the Big 8 played 5 conference games against everyone. So what they would do is play 2 in Norman/Stillwater, depending on whose year it was to be the home team, and then generally play 2 in OKC and 1 in Tulsa. The Tulsa/OKC part switched around off and on, from all 3 in one site to the 2/1 split being different.
When the Big 12 started and it switched to 3 game series against everyone, they kept the Tulsa/OKC sites in favor of the school sites and would play 2/1 in OKC/Tulsa on a rotational basis... usually one site would get Friday/Saturday and then the other would get Sunday. After a while, they started playing 1 or 2 non-conference games at school sites just because Bedlam was/is a big draw in both locations.
Then 'Stache pretty much covers the rest from the past few years when they went back to campus sites for the actual conference games.