Yes. Technical semantics aside, reducing intake enough will make a person have less belly fat, and less gut bulge over time.
I think he literally meant stomach, not belly/gut.
Many people actually CAN shrink their stomachs, because they’ve been used to stretching them out. Yes, the stomach, like a lot of soft tissue, can/will stretch, and the more time you spend stretching it, the better you get at it.
This is how the fairly small sized Japanese guy, Kobayashi, won so many hot dog eating contests. All that practice stretching his stomach to hold volumes the average person simply can’t. It isn’t about metabolism or digestion either, since none of that comes into play over how much you can shovel in, in the short timeframe of the competitions.
Your observations are correct, about portion sizes in the US. Anyone who’s traveled abroad, has noticed three big differences: just how fat most Americans are (it’s pretty blatant, when you’ve been abroad for a few weeks, then touch down at a US airport), how much smaller, average portion sizes are in other countries, and how much more people tend to walk in other countries.
Comments from friends and family from overseas, visiting over here, are similar; “Wow… that’s a lot of food. People finish this in one meal?”.
Even in Japanese/Chinese/Indian restaurants etc. I noticed that ordering the same dish in a local restaurant overseas, vs an American restaurant, the portions in the US are usually anywhere from 150% - 200+%.