Actually, this sort of "no comment" clause in a settlement agreement is fairly common, especially when the case involves a business that deals with the public. The only unusual thing here is that these are tipsters rather than plaintiffs.
But the reasoning behind the agreement is still good. It is a fair exchange for a substantial amount of money. If they feel they can do better selling their story to the news shows, they can forgo the bird in the hand and say whatever they want.
Bulls--t. Wendy's owed them nothing. These people had a moral obligation to do what they did. They were not due a reward.
If my local Wendy's is any indication, they probably lose a lot more money due to slow, indifferent service than they ever did to the finger in the chili.