I'm not sure that Bob Thompson added anything new, but I'll provide an example.
When the Big 12 lost Nebraska and Mizzou, their TV partners were willing to pay them the SAME AMOUNT OF MONEY for fewer teams and fewer games. Thus, in THAT situation, the "composition clause" was not invoked, largely because Nebraska and Mizzou didn't move the needle in the Big 12.
HOWEVER, and you can read between the lines, the "three teams" most likely to leave the ACC are not "Nebraska/Mizzou" level, they are three of the best teams in the ACC and our TV partners would ABSOLUTELY invoke the "composition clause" to pay the ACC less money.
To take the example a bit further...if Boston College, Syracuse, and Wake suddenly (and inexplicably) told the ACC they were leaving, I highly doubt that ESPN/ABC would give a ****. I think they would continue to pay the ACC the contracted-for money (with, perhaps, a PRO RATA reduction for fewer teams/fewer games).
BUT, if Miami, Clemson, and F$U were to leave the ACC, there is no way in **** that ESPN/ABC would continue to pay $35M per school to the ACC, whether for 15 schools or 12. In other words, if the Big 3 were to leave the ACC, you can bet your paycheck that ESPN/ABC will try to come back with "$25M per school for 12 schools".
And THAT would be brutal for the schools that stay in the ACC.
(plus it assumes that only 3 schools would exit, I could see 6-8 schools leaving, with the ACC taking USF and then trying to poach UCF and WVU and maybe even Cincinnati)