It’s all paid for scores, totally made up unscientific crap. A breakfast cereal with lots of added sugar is basically dessert, plain and simple. Fortified cereals are never as good as eating foods the vitamins naturally occur in, and there’s evidence out there to suggest added iron is more harmful than helpful. If you’re going to eat this, do it just occasionally.
If you want 1/3rd of you’re daily carb intake to be from a single serving of cereal giving only 9g of protein go for it. This is why a lot of people have insanely high insulin resistance because before they know it they had 200carbs in just cereal without filling out any real macros. I’d say Nutri-Scores is more like D. Then again Nutri-Scores are complete BS to begin with. But it is from a processed food prospective so I can’t hate too much.