I do that precisely because of the pervading folklore - manifested in your post and the AWB - that LAMEs never make mistakes.
You are either being purposely obtuse or cannot read and comprehend basic English. No where has it been said or implied that LAMEs do not make mistakes.
I would counsel you to read the AWB in its entirety and not concentrate on the spark plug issue. Most of the advice given in the AWB is very sound and should be followed to ensure the longevity of your engine.
If you have the correct equipment to follow the APS LOP method, by all means do so as long as you are comfortable with it and do all that APS teach.