How can operating LOP where internal cylinder pressures are lower, heat is lower, and the combustion chamber is cleaner be worse than operating at 50dF ROP where the OEMs have recommended and heat and pressure are the highest with a dirty combustion chamber? The enemies of metal are heat, pressure and frictional wear--all worse ROP than they are LOP. How do you burn something up when you are running it cooler? Just doesn't pass the smell test, much less data collection. If you can't screw it up as recommended ROP, how can you screw it up worse, LOP in a safer regimen?
As the King of Siam said, "Tis a puzzlement."
****What an engineer would do is to run the engine in a controlled experiment, collect data on the internal runnings, temps, pressures etc. Compare this to the materials, construction of the unit and come up with whether it is more damaging one way or another. This data could then be put into practice and measure the outcomes of operational use from trends and condition monitoring.****
That's what we've been doing for over 15 years! Then we've gone the step further and done it in hundreds of engines in flying machines. Guess what? Conveniently, the data is all the same.