One rule of thumb in evaluating the ceiling of high school kids - especially those in backwater situations like Jackson or Larry Greene Jr. - is that if your scouts have a very different opinion abut a player than the rest of the industry (other teams' scouts, BA, Perfect Game, etc., etc.), that ought to be a huge (or "reaallllyy yuuuuge!") red flag. If your scouts are seeing something nobody else is seeing, the odds are very large that your scouts are simply wrong.
Now, if you have a veteran scout with an unusual track record, I might agree that the risk is somewhat mitigated. But that said, the last thing we want to see with the #8 pick (or with any first/second round pick) is one of those cases where the kid selected is simply "off the board," in that everybody else in the business finds the pick puzzling.
Later in the draft - not such a big deal. If the Phils want to take a gamble with pick #83, on a high school kid who their scouts value more than other clubs (or on somebody that nobody else thinks will actually sign) - I'm OK with that. That's Lucas Williams, Cord Sandberg, Dylan Cozens territory. But in the first round? No, thank you.