I responded to "WeekNight Ace" with what Doc said above. Here was his response:

That's fine. But why one set of rules for league play as clearly written in the rule book, and then another set of rules for conference play? Also, if you don't mind, please provide a link for the conference play rule. Thanks.

My point still stands. If the pitch must reach the back of the plate to be a strike but the batter is allowed an unlimited forward step, then there is no low strike. Why write a rule that effectively forces a pitcher to throw a belt-high pitch to be a strike?