The important piece you are missing is understanding how little the shaft flexes during the incredibly brief tip contact time with the CB. Most of the flex happens after the CB is gone. It might help to do a little more "homework:"I'm not the PhD in the forum. But I do have my own evidence. Just because I'm not doing science doesn't mean I can't judge the lack of science or understanding. There's obviously room to improve our knowledge of shaft physics but God only knows why everyone has their head in the sand
I know you said you read everything at the last link, but I doubt it based on your beliefs. Please check out all the info, explanations, illustrations, videos, articles, analyses, and links on that page if you want to improve your understanding. It doesn't help to keep spouting off anecdotes and idle challenges if you don't first have an understanding of the important principles.