The auto 1st down on all PFs by B has been on the docket a few times, but never made it to the floor for a final vote. IMHO, two major reasons : (1) As GoodScout posted, it currently treats foul on a defenseless player as more severe; (2) If all PFs were AFD, it would only benefit the offense and some would push for LOD if foul by A/K.
Regarding #1, then why isn’t blindside block, targeting, and hit on a defenseless receiver also an AFD? In the context of the NFHS preferring to avoid exceptions, it doesn’t make sense to single out the “roughing” fouls as being worthy of an AFD but not the other ones I mentioned. Heck under the current rule a B player can punch an A player in the face and be charged with fighting and disqualified, and it still isn’t an automatic first down. How does that make any sense?
Regarding #2, if A commits a live ball personal foul on 1/10, their next play would be 1/25. If B does it, A’s next play is still 1/10. If instead A’s next play was 2/25, which is a drive killer at the HS level pretty much. I would argue that unbalances the scale of offense vs. defense in the opposite direction.