the notes system is flawed

Just won a game with Twitch, 33mnts, my stats 18/5/10(out of 37 team kills), my damage to champions 33k, 10k over the second damage in the game, most gold earned in the game aswell. Results in A grade and 2 of my team members got S grade, both bellow 23 team kills participation(80% of which assists), less gold earned and far less damage done, ofc 1 of them was tank and had high damage taken. I dont question why they get S grade, they deserved it, but so did i with the superior stats achieved. The only weak point i can guess is i had low CS, but this was duo to my high kill participation, which to repeat resulted in the highest gold amount