If there's an operation that usually (though not always) finds its way to the public at some point, especially for players like Brady or Moss. I recall news a few years ago that Brady had played most of the year with a sports hernia after that season ended.
I can think of a couple of reason for still keeping the information private though. For one it could be used as leverage in upcoming free agent negotiations. An agent negotiationg on behalf of a wide receiver is going to be more aggressive for a bigger payday for his client if he knows that not just Welker, but Moss is also hurt and will be undergoing surgery. Take that information away and his contract demands may be a bit lower.
The other reason is this: why bring more scrutiny to the team by Goodell and the NFL front offices in the way they handle injury reports? If the team reports injuries to Brady and Moss that may have lingered all season long, who's to say they won't be fined? Don't forget the Jets were fined well after the fact for Favre's injury last year. Goodell is very intent that the gambling industry knows as much as possible about player's injuries in the name of integrity.
