"The only thing you really need to know is that you should be eating fewer calories than your body burns everyday. If you do this, you will lose weight – it’s science. Nothing else matters for weight loss"
This may be one of the most harmful statements about diet. It's mostly true, but in a fairly banal sense. A baby will have a caloric surpluss as it grow. So will a potato. Without the calories, growth will stunt. This is the trivial fact.
The growth trajectory of a potato or baby is not trivially determined by caloric surplusses. One big factor is genetics, which tell babies and potatoes to grow. There are environmental factors, many of which are calorie related.
"This is a scientific fact" is in the context it's used, an empty tautology. Caloric surplusses can be used in exactly the same way to "explain" why an elephant is bigger than a mouse, why there are 6 billion people on the planet, how a bodybuilder got his biceps or why you got fat. This makes it a nonexplanation.
A less abstract hint that we're dealing with a nonexplanation is apples. Add one apple a day to your diet, and calorie counting will tell you that amounts to 5kg fat per year.
We know from experience that people do not gain/lose 10 lbs per year by adding an apple a day to their diet. Your apetite or metabolism (these are related) will compensate for the apple.
That doesn't mean that intentional caloric restriction isn't a good method. It works well for some. Other things work well for others. We don't have perfect knowledge about what works "in the wild" or even in the lab.