Champion do not tell you NOT to test their resistance for two reasons; You should be doing what they (not their competitor) tell you to maintain their plugs and if you buy another $70 plug because you didn't that is their gain.
No. Degradation of performance tells you, Not Champion. They suffer degradation, and pretend it does not happen. Amazingly it is a direct correlation with a known causation. The fact a competitor has latched onto it does not alter the facts.
They have head buried in the sand on this and some other more serious matters that will not be discussed openly here.
Once discovered, it is obvious. A bit like fairies in your garden, they do not exist. Until you discover they do. Then what?
I would not have believed it several years ago. But data is hard to argue with, especially when a bunch is collected by yourself. I have never found one engine yet that runs smoother with high resistance plugs. Not one.