I am not blaming anyone, I'm merely stating that the "because I said so" reason works well with my 6 year old daughter to teach her right from wrong, but most of us adults like hard facts of "why". Why not regulate valve lash, or prevent lapping of valves since it does actually change the make up of the valve and head ever so slightly? Both of those activities provide performance gains.
In reference to boring a carb, you state, "The removal of material does contravene the rules but not provable unless out of spec". To me, this statement endorses the breaking of rules as long as it cannot be proven that you did so.
I guess your "why" is because it is not the intended stock of the motor. And to many that is a valid and acceptable answer. I just find it interesting that it is specifically forbidden in the rulebook yet does not enhance performance and/or have safety concerns. Exhaust retainers and catch cans have specific reasons from a safety perspective even if there is no performance gain.
I, myself, know how to and take all my motors apart before I build them and all my motors have the arrow on the piston pointing in the direction it is supposed to. But I was not always as savvy as I am now, even if that is still amateur compared to the pro-builders and those with 20 years under their belt.
Please allow me to complete this post by simply saying that this is healthy debate. I am in no way accusing nor attacking anyone of their interpretations of "Box Stock". I ask for help from all you good people way too often on this site to voluntarily try and tick any of you off. Thanks for letting me rant.