The article @BoxingRobes posted uses RB's NFL weights - https://www.footballoutsiders.com/projection-points/2020/running-back-growth-potential-starts-size
So that 29-31 optimum BMI is for NFL RB's - it's not using what those RB's weighed in High School.
You're confused & incorrect on both posters & data
Your discussion/data is literally meaningless if you continue comparing 16-17 year olds weights to 21+ year olds weights and this is why I and others have shown that HS measurements don’t have the same correlation to college success.
While you did not post the article, you it indicating you implicitly agreed with the poster stating 29-31 BMI as a “sweet spot” for RBs. Again, meaningless because it is geared towards the NFL and players professional weights.