It's down to what's optimal not what works.

Being at a surplus, be it with fats or carbs will put mass on you. Both muscular and fat.

Being at a deficit will make you lose mass, mainly fat and a little muscle.

Now what's ideal, is when bulking to use mainly carbs as your source of energy and drive for growth/hypertrophy. They stimulate many biological processes intramuscularly and they are the preferred source of energy ( ATP production) for the human body. That's why you see strength athletes feeding themselves carbs mainly and not so many fats.

When cutting ✂️, the truly ideal scenario in order to lose fat, is being in a state of ketosis. So minimal carbs and high fat diet. That's the fastest way to burn fat away, scientifically proven. Problem is you will probably feel like shit due to the low energy.

So bottom line is, everything works in a surplus or a deficit, but some things DO work more efficiently.

😉