Yeah I've heard of that as well. I think the theory is that you're only giving your body one fuel source at a time, so the other type can't be stored as fat. Sounds very bro science-y.
The recent diet trend is to carb back load. So no carbs from breakfast to lunch. Then you consume 25% pre workout, and the rest before bed. The theory behind that one is that your insulin sensitivity is much greater in the morning, and much lower post workout. I'm still waiting on seeing any type of evidence before giving up my breakfast carbs. Sounds like a miserable start to the day.