"Scrubbing" think about it. Full weight on a tire at 80psi will have a lateral drag of a certain amount. Lighten the load and it will be less. Heavier duty tire with the pressure set to say 65 will not scrub anymore than the 65psi "D" tire. More weight equals more scrubbing along with softer tire sidewall of a "D" tire.
I highly doubt your outer edge wear is related to scrubbing and is more a case of the tire is simply not carrying the load to allow it to wear un evenly.
I know I won't change your mind but when one of the largest tire manufacturers says to use the chart when upsizing load range I have to believe it as so. They said to do so will give even tread wear, better stopping and better ride. I used their recommendation and it proved to be correct.
JIMNLIN has a lot of good info but remember he comes at this from a commercial haulers perspective.
I would like someone to explain whey they have weight inflation chart for the ENDURANCE if it's not ok to run tires pressures based on actual load.
I have the 14" "D" ENDURANCE 65psi tires on my Boat trailer. I have ran them since Summer 2017 at 50psi based on load. They have a perfectly even tread wear. I have ZERO edge wear from scrubbing. It get's "SCRUBBED every single day of the Summer on a chip seal rough surface.
