6pt,
I can't fault your thinking as a lot of people will agree with you. In fact in the SS game they think a little tipping doesn't hurt accuracy.
But I tend to disagree with both points. How do you, or they, know this for a fact if you don't know how the accuracy would be if these factors weren't included? Say... Take one of your gc bullets that you know the accuracy of and have it made into a PB one.
I look at it as how can anything that changes the flight of the bullet, even slightly, be good?
You've said in the past that you'd like to see cast bullet accuracy in the .4's. I assume you get the CBA magazine “Fouling Shot". If so look at the match results from the different clubs. You will usually see that the PBB shooters are at the top of the lists, or very close to it. Of course many factors determine the winner but if that's the case then only good shooters shoot PBB.
I will be trying to prove this GC point sometime this year... hopefully.... as I have a Lyman 225415 GC mould that's been converted over to a PBB. Should be an interesting line of experiments.