contracts that conferences are signing now no longer have tier 3 rights (except for a few very minor exceptions). All excess inventory that doesn't fall into what we used to call tier 1 or tier 2 rights are now included in the base TV contract. Those games show up on the SEC network, ACC Network, B10 Network, ESPN+ or one of your P12 regional networks.
BYU's existing contract is actually better than many conference contracts (like the P12 and B12) where the marginal games are buried on some regional P12 network station or on ESPN+. Since we went independent, there have been 2 home games that ESPN didn't pick up for a broadcast (in those cases we produced them ourselves on BYUtv).
Bottom line is your thinking is in line with the old tiered system of TV contracts. That doesn't exist any more. Every game is included in a conference's tv packages.