Due to the design & shape of flakes, pellets are generally more nutrient dense, and more stable in water. (as in less nutrient leaching compared to flakes) This is not my opinion, but a fact that has been stated by some of the leading researchers in aquatic nutrition. Also flakes typically have a higher percentage of binding agents than pellets, which equates to more carbs/starch than pellets made by the same manufacturer.
So while one can certainly feed their large 10+ inch fish flake food, it certainly isn't an overly efficient way to go about getting optimum nutrient levels to ones fish.
This^^^
And, do you think your fish will consume all of the flakes before the filtration gets them?
Also, try ocean nutrition and you will see the difference in flake food.