The basic details including that each school would forfeit their home TV earnings are in black and white...all from reputable sources...google it.
That doesn't really make logical or legal sense. A legal agreement wouldn't be valid if one party ceased offering consideration to the other.
Right now, the Grant of Rights is an addendum to the television agreement. What is being offered? The team's rights of televising their home games is being granted to the conference for a set period of time rather than just the period of time in which they are members. What is being given? In return to those rights, teams are compensated by the conference an agreed-upon share of the television revenue.
The agreement has to be fulfilled on both ends in order to be valid. If a team leaves to join another conference, the old conference still has to honor the consideration (in this case, compensating a team for those rights). It can't just say "we get to keep your rights but you don't get paid for them." That would be a breach of the contract.
Think about a singer that records 10 tracks for a record label under an exclusive contract. They release the album that was contracted. Ten years later, the label, which has a grant of rights to the recording, releases another album with re-worked tracks based on the original recordings. That artist is still entitled to the royalties despite being under a new exclusive contract with another label. Likewise, a school does not forfeit its right to compensation just because it's granted the rights to a conference. It didn't grant the rights for free. It's granted under the condition it will receive consideration for those rights.
If a team leaves the Big 12, for instance, it will still be entitled to its share of the Big 12 media revenue (although it would no longer get bowl revenue, NCAA units or gate sharing). The deterrent comes because the new league would not have a right to televise those games, and instead, the revenue would be split equally among Big 12 members (including the school that left). So the new league would have to work out an agreement with the school that it's willing to forfeit that revenue as a deduction against its new conference revenue distribution.
The Grant of Rights isn't intended to be punitive against a school. It's meant to make schools less attractive to conferences seeking to take them. The schools will still be entitled to compensation in exchange for its television rights wherever it goes. The only difference is that the conference retains those rights and obligations that come with.