Former NFL player Michael Oher claimed that he was never legally adopted

My thoughts I never really care about his story. Didn't even watch the movie or watched any documentary of his life. His life's story is like 10 years old or something. Don't know but if he is saying this now, why he didn't say it then?
He only discovers it earlier this year. He thought he was adopted until then. He said there were some things that didn’t make sense but with his career taking off, he was focused on that. Only after the his lawyers were looking into some of his contracts did they discover this and explain to him what it means. He was told by the family the legal agreement was the same as an adoption but it was really giving the full rights to his name and any money made from it.