Manny made that rule up first, actually. Same with the 8 oz gloves. Floyd agreed to both without hesitating, because one thing Floyd has never been is a prima donna at the negotiating table. Now, Manny on the other hand..
I doubt Floyd cares much to fight Manny. He's happy to let Arum milk Manny and probably figures Pacquiao will decline, with him being a fighter that takes more punishment. Then when Manny slows down, and the IRS and creditors come calling on Floyd, then Floyd will be happy to fight him. Fuck Floyd, Arum, and to a lesser extent, Manny as well.
You're not serious, right? Do you not recall Floyd abruptly bailing out of talks for a DLH rematch and instead sitting out for nearly two years? One guess for the reason the fight didn't happen...