Setting up an entire diet based on percentages just doesn’t make sense. When someone places protein, carbohydrate, or fat requirements in terms of percentages (40:30:30, 20:50:30, etc.), it doesn’t really have any relevance to what that person actually needs.
A diet consisting of 30% protein may be too little for someone who eats only 1,000 calories per day, and too high for someone eating 5,000 calories. With this type of planning, someone who “needs” 150 grams of protein would only be ingesting 75 grams per day on a 1,000 calorie per day diet, and 375 grams of protein per day (more than double what he “needs”) on a 5,000 calorie diet.
Additionally, many diets are often slapped with a “high carb” or “high fat” label whenever a specific macronutrient is over a certain percentage. Most dieticians would be quick to label a diet consisting of 35% fat as “high fat.”
However, if we took a 2,000 calorie diet with 35% of calories coming from fat, and added 200 grams of carbs (800 calories) without changing anything else, the total calories are now 2,800 and the “high-fat” diet suddenly becomes a “low-fat” diet, because the percentage of fat dropped from 35% to 25%, even though total grams of fat stayed the same.
Save your mental energy for time under the bar, not nutritional mathematics. There’s no need to worry about trivial minutia such as macronutrient percentages.