Boras gets his clients the money that they feel they deserve. No weapons are brandished during negotiations, so it is not his fault he gets the huge contracts he does. The owners are willing to pay for his clients and do so.
This said, the timing of the announcement was just more of him putting himself above the game. He is a great agent, but his "schtick" is very old and tired. There are dozens of people that can do his job and most have more respect for the game that pays their salaries than he does.