The math is a lot harder than you think and you can go into a deficit by eating more
Here's a metabolic ward trial:
…patients…were put on to 2000-calorie diets of normal proportions to show that their weight could be maintained while in hospital at this level and then placed on high-fat, high-protein diets providing 2600 calories per day. It was demonstrated that these patients on the whole could maintain or gain weight on 2000-calories but, except in one instance, lost weight consistently on a 2600 daily calorie intake.
This matches my own personal experience. It's not just about how much you eat. It's much more about what you eat (and other ways of changing metabolism, like IF). I lost body fat by eating a stupid amount of calories (regardless of activity level).
You can't just calculate a generic BMR and then try to stay under that. It's irrelevant and the reason many say they can't lose while in deficit. Your body adapts too well to what you eat.
Hormones drive the system, not just volume of food.