You didn’t answer the question. You just added to your side of the argument without basis. Even if it does not roll or if it does for that matter, you have not posted any proof, hypotheses or research to back up your claim. I’m pointing out that common sense tells that there is a roller tip on it with the intension of rolling across the tip of the valve. How much do you think it would roll if it does work considering the contact path on the valve tip has to be less than 5/16 of an inch? Common sense should tell you there has to be some rolling loss (scrub/sliding) due to friction and pressure.
