While I don't agree, I called and spoke to a member of the NFHS rules committee. He is a personal friend and he is also one of the 4 IAABO national interpreters (and I know that means nothing to some here
). He told me the rationale for the ruling is that the player straddling the line is simultaneously the last person to touch in the frontcourt and the first person to touch in the backcourt and therefore this is to be ruled a backcourt violation in NFHS. For the record, he disagrees but said he has been overruled on this discussion many times as it is a question that is continually submitted.