Leadballoon
A complete misunderstanding of what caused the cracked spark-plug insulators.
In your opinion. Now for the facts:
If the engine has detonated visual signs like broken spark plug porcelains or broken ground electrodes are dead giveaways and call for further examination or engine disassembly. Engine Basics: Detonation and Pre-Ignition by Allen W. Cline
The typical cracked core nose condition shown may be caused by improper cleaning or gapping procedures and by detonation. Champion Aerospace Aviation Service Manual
Detonation is an explosion of the combustion charge in an uncontrolled sudden manner. This condition may damage the spark plug electrodes or crack the insulator nose as well as destroy the engine if permitted to continue. Tempest Aviation Spark Plugs
It is a fact that detonation causes cracked insulators. It is also a fact that running lean of peak at high power puts an engine inside its certified detonation envelope. Note I am not saying LOP causes detonation, I am saying LOP at high power can cause detonation, for instance when a pilot forgets to set the mixture full rich before take off or go-around on a hot day.