The Cavs/Wolves situation was interesting. Everyone knew Wiggins was getting moved, but the 30 day rule prevented anyone from publicly talking about it. It was Brian Windhorst who broke the news prior to the moratorium ending.
"The deal is done, but not done," Windhorst said. "The teams have agreed, but they can't say they have agreed and they can't agree because we are in this weird moratorium period. Because you can't trade Andrew Wiggins until the 23rd of this month."
Technically, there was some incentive for them to keep it on the down low:
Windorst says that in the period before the trade can become official, it is possible a team could swoop in and get Love with a superior offer.
This was less of a concern for the Cavs, though, since it was unfathomable anyone was going to outbid an offer of Andrew Wiggins for Kevin Love.
Here's an article about the purpose/effectiveness of the 30 day rule for rookie contracts:
http://midlevelexceptional.com/2014/08/26/exploring-the-30-day-rule/It's still possible Noel is talking out of turn (once my video got to him he removed the twitter profile pic with the hidden message and replaced it with the cryptic movie still about "real men handles business"), but it's true that Jaylen Brown signed on July 28th and we're in the midst of his 30 day no-trade period. So if the Celtics have any inclination to move him for Noel, in a package for Blake Griffin, Jimmy Butler, or whoever... it can't happen until later this month even if a deal has been agreed to hush-hush under the table.
There's some cap-matching logic to waiting until after the contract is signed to deal away your rookie. Once the 30 days are up, his salary can be included in the deal.