I'd be interested to hear a bit more about this method. I've never done it this way before, I always have assigned percentages, it makes my diet feel a bit more structured to me.
But what your saying, for instance, is if I was on a 4500cal a day diet, at 205lbs, to assign a minimum number to protein that's sufficient for muscle growth, which is what, 300? Then a minimum number for fat, which I'm really not sure how you would decide on a minimum number, typically fat intake is directly related to carb intake, at least in all the diets I've ever done. If your carbs are high, you can lower your fat, however if your carbs are low, you need to increase your fat. How would one assign a minimum number to fat?
But just hypothetically speaking let's set fat at 125g a day. That's about 1400 cals between both fat and protein, then I could take in 3100 cals all from carbs equaling about 775g of carbs? And I would stay just as lean on that as if I followed a 40/30/30 split of 4500 cals where protein was all the way up to 450g, but carbs were only about 330g instead?