They're good numbers for an average player, and I, admittedly, do not have access to, nor have I studied, the all-22 film, which is the only film that matters, not highlight tapes. I doubt many on here watched the all-22 either.
I haven't watched the games either, but it might be possible to deduce a few things. Game 1 was vs Homestead, Palmetto was up 28-0 at halftime. My guess is Palmetto pulled their starters early since they didn't score again until the 4th quarter (final score 35-7). I can't tell if palmetto scored two TDs early in the 2nd and then the coach pulled his starters before the end of the 2nd quarter or if he played the whole half. So his numbers might have come in only 9 quarters of football (almost certainly no more than 10 quarters).
The score vs. Dr Phillips was 10-0. It doesn't appear that either team was throwing the ball, so that would mean sacks would be hard to come by.
HS football might have changed a lot from when I played, but back in the day we ran a Veer offense and rarely threw the ball. It doesn't matter how dominant a defensive lineman was, the stat sheet wasn't going to show a lot of sacks. If the QB was reading his key correctly, the DT wouldn't have many tackles either. However, he could have totally dominated the game without it showing on the stat sheet because he was penetrating into the backfield so fast it effectively took away the FB dive, which significantly reduced the offense's ability to move the ball.
I don't think someone can say he underperformed without a whole lot more context because it's possible he had a huge impact but it's not on paper (and as far as I know, HS stats don't track QB hurries so he could have been disrupting the offense significantly).
It's also big big difference between criticizing Pickowskis performance and a DTs performance. A QBs stats generally speak for themselves (there may be cases where a QBs numbers look significantly worse because the quality of the team around him is so bad but those are exceptions to the rule). On the other hand, I imagine you've seen enough football to see a DT totally blow up a game plan even though he doesn't put up great stats on the stat sheet.
17 tackles, seven TFLs, a sack, a forced fumble, and three pass deflections in just 2.5 games looks rather dominant to me (but I can't fairly judge until I watch the games)