Beezer- Regarding his birth date, he was going to be a legitimate senior when he jumped to USC. The cut-off in California is up to January. Kids are recruited and drafted by grade, not age. Plenty of others that started college at age 17. He had three years of high school baseball. Sorry if you don't agree or get it.
Bear- He's 18 and a half and listed at a generous 6'1. Where do you get possibly projected at 6'3? The rest of your post is, well, interesting.
This kid has been hyped by people for years since he was 14. Ever heard of Andy Beal? Top player in the country for his age when he was young. He's now an average college guy. Some of the top young players in the country (Baseball America's Players For the Ages as the best resource I know) turn out to be average , good players. I've seen it for years and I don't think it helps these kids to be hyped so early.
Stock is a good talent who made a good decision for himself based on his situation. He was a smart kid who could handle college-work and would be more prepared to play professional baseball with three years of college under his belt. I bet he does just fine at the next level. That said, there will be plenty of players HIS AGE that will be as good or better than him when all is said and done. That's not to detract from his ability- it's just that young players mature and progress at different rates.