This doesn't sound like it was controlled for simply eating less calories.
I can assure you "everybody" doesn't already know that, in fact, this seems to be a _minority_ opinion.
The vast majority of people seem to think they need a diet (i.e., restriction on type of food) to lose weight. The only people I know who are actually on CICO are people I encouraged to try it.
They underestimate how many people literally do not believe that eating at a caloric deficit would result in weight loss.
1. Utilizing stored calories (which will result in weight loss).
2. Expending less energy (which would not result in weight loss).
Realistically, reducing calories probably results in some combination of the two, with things tilting toward expending less energy as your body gets below a body fat percentage that it "wants" to be at.