You are right if winning at the high school level matters.
MLB has about 8% of all runs scored are unearned. College is roughly twice that. I have no idea about high school but would guess 1/4 of all runs are unearned. That makes a strikeout pitcher more valuable in high school. That pitcher can give up many walks as long as his strikeout ratio is greater than 3:1. A MLB average is 2:1.
I ground ball pitcher is more valuable as one plays up. You are right about the MLB stats not meaning as much in high school. Ground balls in high school produce unearned runs, in college and above they are usually outs.
My son always had a high WHIP but low ERA. His K stat was 1.4 per inning from high school to pro ball. This was too much. I tried to talk him into striking less out in college and pro ball but he hated contact. He was not made for pro ball with his mentality.
I will say those who ignore stats as a coach, are not doing their job. The player doesn't have to be paying too much attention, but the coaches better.
If you study MLB, the stat that explains runs scored more than any other is OPS. Batting average is not even close to this stat and is over-rated as a measure of a good hitter. IF OPS is the best measure to look at runs scored and offense, I suspect OPS against is a good measure for pitchers. However, the coach that adds errors to this is on to something for a high school stat. (He posted earlier.)