Seems like he pretty obviously has leverage.
I'd quibble and say he's getting what he wants, but doing some because it's a win win for him and the team not because he's leveraged Baltimore into something. But if both parties wanted to play this the whole way down the line, the Ravens would easily win. He can't hold out all year because he woudln't accrue a service year. And if he stays and plays lazy, he'll never get the FA deal that reflects the value he'd at least have today, IMO.
I guess you could argue his leverage is that teams will pay him no matter what even if he plays poorly next year. But that feels more risky to Brown than leverage.