There's no "mistake". GM lied, pure and simple. As per usual he drowns stuff out with a conveyor belt of "tweets", comparing himself to the clown in the WH (there are similarities to be fair, they both talk crap) and acting as if he's a martyr. The fact is he was just dishonest, got caught out and it's hardly the first time either.
You need a healthy dose of 'Fox News.' Hopefully, that'll straighten ya out?