I suspect he was put up to this. Either the creator or Bitcoin asked him to do say it was him, or the creator is a group of people and he is one of them.
No, he’s a well known flake. I have no idea what benefit he thought he’d gain from this, but he did get a moment in the spotlight.
All anyone needs to do to prove he or she is Satoshi is spend or move a single bitcoin out of that initial million.