Obi is 17, and the post you quoted was about a different player making the step up at 17 in the championship and commenting on the huge difference.
Players making that step up from youth levels to the PL first team at 17 doesn't happen as often as your post implies. Yes, academy products progress to PL first teams every year - but they're not often as young and inexperienced as Obi. They're usually at least a year or two older, often with some loan experience in senior football.
It's rare to see someone as young and inexperienced as Obi step up so soon. And it's more to do with the dire state of our attacking options, rather than a nailed on confidence that Obi is an exceptional talent ready for the PL at 17 and 3 months. He's an exciting talent with good potential, but there's no way he'd be being promoted this early if we weren't in such a desperate position regarding our attacking options.