Not to say you're wrong, but one of my buddies freshman year of college was big like that kid. He had a HUGE chest, 18-19" arms, and the rest of him was pretty big too, on a 5'10 frame. And he was all natural, although he'd been lifting since he was 12 with his father (also naturally big). He was actually pretty poor growing up so his "supplement" was skim milk, a gallon a day.
But I understand where you are coming from. There are guys who are so obviously on some form of steroid that its not even funny and they'll deny it to their dying day. Its a self-image issue, they feel the need to be that big to impress girls/other guys, but because of the bad stigma steroids have they'll refuse to admit they use. Just the way it is.