That statement is true in the most pedantic, literal way possible. It's also completely and utterly useless to someone trying to lose weight, since nobody knows what their calories burned number is or how it will change in response to a change in diet or exercise (or climate, or stress, or sleep, or illness, or monthly hormonal changes, or literally anything else).
Yes, you're correct that you can look at literally 100% of people who lost weight and say "they ate less than they burned!!", but that doesn't mean that telling a fat person to "eat less than they burn" is in any way helpful, since the only way to determine how much you burn is to keep track of your calories in and how much weight you've lost over a particular time period, then calculate your burn rate after the fact.
It's like someone asking you how they can make money, and you tell them "It's simple math, you just have to buy low and sell high, you fucking retard!"