The point was that a high traffic green would reduce the accuracy to a low percentage. Pelz putter would make every 10 foot putt on a perfect green assuming a round and balanced golf ball. On a normal green after a day of play not so. Meaning that putting for most of us involves a high percentage of luck. Something that is important to understand.
Scientific fact and observable fact are the same thing.
To my knowledge based on what I remember reading trying to put topspin on a putt is not the best way to putt. Maybe someone else will care to comment?