It definitely can be the case. Absorption of calories depends on the person so the same people who eat 2k calories could get roughly 2k calories OR LESS depending on the gut bacteria and other variables.
I do agree with you on people's reported caloric intake. Most people inaccurately record their eating habits. I use an app to get an idea of what my day was like.
Nutritional panel information is not an in vivo measurement.
If you put 100g of broccoli in a bomb calorimeter and burn it in pure oxygen, you heat it up by 34 kilocalories.
If you put it in a human digestive tract instead , the human can absorb anywhere from 0 to 34 kilocalories of food energy from it. We already have ample evidence that the food energy absorbed may be affected by the microbiome in the intestines, the preparation method used, the time of day, the time of year, and other foods that may have been eaten at around the same time.
But the calorimetry does establish a hard upper limit on absorbable food energy.
This is why non-ruminant herbivores with shorter digestive tracts--like the arctic hare--will engage in coprophagy. They will eat their "first-through" turds, because there is still some food energy in them. Ruminants do essentially the same thing with multiple stomachs and regurgitation.
If you aren't weighing your food and burning your poop in a calorimeter, you are inaccurately reporting your caloric intake. Even then, you can't really know for sure how much of that energy was absorbed for use by human cells, and how much was used to sustain your microbiome.
No matter what conditions you may have (or think you have) the above method will tell you exactly how much your total daily energy expenditure is, including what passes through you that you don't absorb, so you can know how much you need to eat to lose, maintain or gain.
I do agree with you on people's reported caloric intake. Most people inaccurately record their eating habits. I use an app to get an idea of what my day was like.