By Tzvi Machlin One of the key gripes the Cleveland Browns are believed to have with quarterback Baker Mayfield is a lack of maturity. A point of contention during today’s introductory press conference for Watson came when owner Jimmy Haslam was questioned. He was asked about an alleged comment where someone in the organization called on Mayfield to be more of an “adult.” But Haslam denied that any such comment about Mayfield was made by ownership. Though he didn’t state whether it came from someone in the organization. It seems like that the “adult” comment was an excuse for some other gripe …