It may sound like sour grapes but he does have a point. The Browns trainers and staff clearly did not do their job thoroughly enough. When you get hit like that there's no way you should be allowed back into the game until you sit out long enough to run through all the tests.
Harrison's tends to lash out when he's under scrutiny by the NFL for something he did in a game, I'll give you that. He may not come right out and say it all the time but things like this can seem like he's just whining but league should have probably fined the Browns for letting McCoy back in the game.