So if I believe this, don't I have the knowledge of an experienced
person about it?

Yes you have the knowledge but without experience to evaluate it, that
is the issue that I have with inexperienced people passing along second
hand "knowledge" as "fact".

I have the experience to know that a kellet will not increase ultimate
holding power of an anchor, nor will it significantly decrease shock
loads under the conditions where it is important. I know from
experience that even a 3/8 chain rode will be pulled bar taut with
approximately 1200 lbs of pull on it. Once the rode is bar taut, a
kellet is worthless. A kellet is useful for reducing swing radius in
light to moderate conditions. Period.