ALF -
The "Try for Point" was added way back in 1876 with the rationale being as "a method to break ties"
One could argue, (and one has) allowing the Defense to score on a Try further enhances the same rationale used in 1876.
Can't speak for the EXACT rational notion back in 1876, but it's reasonable to presume that the "TRY" may have BOTH been created AS " a method to break ties" by giving a scoring team an EARNED REWARD OPPORTUNITY, "for scoring a Touchdown".
If you are convinced that changing the NFHS rules to accommodate the ability for the Defensive team to score on a try, would somehow significantly enhance, or particularly improve Interscholastic football, you should consider appealing to NFHS to do so through existing channels.
I would doubt there was much of clamor, or burning need. to add this possibility to the current NFHS code, although, you never know