misinfo. that has nothing to do with why athletes train the way they do. getting more calories in is not a limiting factor.

anaerobic lactic and alactic regime training just has a hard metabolic and fatigue thresholds where you won't see any improvements if you add volume.

aerobic regime training (which is by its nature low intensity) does, from what we know, not really have the same limitations. on the contrary a lot of its most important adaptions keep increasing with absdurd training volumes and only show up after accumulated years and decades of training (long distance endurance athletes can often peak or maintain near peak shape into their 40s or 50s because of this).

all of this necessitates large volumes of low intensity training.