Those foods you ate are all more calorically dense than plain potatoes so my point still stands. It's not about the calories but the total volume of food that the human gut can process in a day. Have you seen 13 pounds of potatoes?
Potatoes are ~0.7kg/L, so that's ~8.4L of potato over the course of the day & 370 grams per waking hour, which is one big potato.
Yes my examples were somewhat high energy density but in the second example, I probably had 3L+ in my belly in just one meal. Honestly I think your body just gets used to it.
I'm not familiar with the 13 lb of potato claim, but it strikes me as a stretch (hah!) but not inherently implausible.
