The engines should be exercised to full throttle routinely. It is best to allow the rack and injector unit / governor to run through their full motion.I’ve never seen an official requirement from CAT about running the engine at WOT other than its expected a certain amount of the time.
I think idling around for extended periods without getting into the power band with the turbo producing boost is just as bad. I don’t think you need to go to WOT to achieve this, just a good run inthe usual cruising RPM range 2000-2400.