Too early to figure out who the Twins should pick.
However.The last prep pitcher who was drafted 1-1 and signed, was a "cannot miss prospect" like Hunter Greene is.The immortal Brien Taylor, lefty mind you. (Great retrospective on that signing here.A must for any Greene fans.)
The competition that high schoolers are facing is about 5-10% (at best) of what College pitchers are facing (and this assumes that 1 of their opponents will make it as a starter in a College squad, which is not really true.)And if one has a 98 mph fastball as their only good pitch, he can fool a lot of high school kids....
The take-home message from the article you linked: If the Twins take Greene, the most important thing is to make sure he doesn't tear his rotator cuff while defending his brother in a bar fight.
Personally, I don't think the competition quality for high schoolers is very important, particularly for pitchers. I'm very confident that professional scouts and decision makers are not judging Greene's abilities by his box score stats, but rather are judging this tools and projection. But even beyond that, Greene (and almost every other top high school prospect) spent a lot of his summer playing in showcase tournaments around the country. Outside of the top-tier of the SEC, not many college players have the opportunity to play against a dozen or more potential first round picks like the HS players get to in these tournaments.
Also, I'm not sure how much weight to put on secondary pitches (or lack there of) right now. How good were Kershaw's secondaries coming out of HS? I know that was the big knock on Bumgarner going into his draft. At a certain level, the selection of a HS pitcher is a bet on the projection of their tools: arm strength, athleticism, build and work ethic. I'm not sure how much present-day stuff and results factor into that.