You can't remove 500 boys that "don't play football." Remove 500 boys from Oscar Smith High randomly, then see what you are left with. You likely still have a powerhouse program, but the law of averages says you don't have anywhere close to that depth which is present. Otherwise, 3A schools would regularly beat 6A schools in the state of Virginia. They regularly don't beat 6A schools for this very reason. And....if going by your argument, then Bland County should have no issues matching up with Oscar Smith.
As for Franklin County. You are cherry picking. There are ALWAYS outliers, ALWAYS exceptions, and its to easy to find the one exception, and then write about it, but the law of averages SAYS, if all the 6A schools play all the 3A schools in Virginia, guess who is going to win the overwhelming majority of those matchups? You know the answer and so do I. Otherwise, throw out classification systems and just declare one state champion. Indiana High School Basketball did it for a long time. Yep, we talk about Milan High (Hickory-Hoosiers Movie) which was the exception. The overwhelming majority of those state titles until Indian reclassified was coming with schools with over 2000 kids, or simply put, the larger schools.