This doesn't really prove much of anything. It was too short of a "study" and doesn't have enough participants or enough controls to determine much of anything, except that if a person reduces their calorie intake, they may lose weight. I'd even venture to say "probably," but I also know "not necessarily) is also true for many people.
I can lose more weight on low-carb than on the same calories of high-carb. So I can lose more weight and feel fuller on low-carb than high-carb diets of the same calorie level. That doesn't mean I can't lose on a high-carb diet, but why would I want to (especially when I also know that the high-carb diet triggers or worsens some health issues and symptoms).
I only know this because I played lab rat and scientist with my own food journals. I would never lose weight on 1800 calories of junk food, for a variety of reasons, but mostly because when I eat junk food I can't stick to 1800 calories. I end up feeling starving and eat much more.
Some people do seem to be able to eat a whole lot of crap with no apparent ill effects (although apparent may be the key. Just because they look ok, doesn't mean they are).
Anyone can use a food journal though to experiment with different diets and see which they like best, and which they are able to stick to best, on which they feel the best...
But this one guys experiement raises more questions than it answers. Would he have lost more weight if he had followed a different diet of the same calories? How hungry was he on this diet? Would he have been less hungry on another diet? Did he experience any problems on this diet not related to weight such as headaches, concentration levels, sleep quality, emotional stability - was he crankier? Did he enjoy the diet or was it a torture. How long could he have kept it up without going bonkers?