Agree - although I think identifying desired aggressiveness is tough - for example, you take a kid who's got great skills, plays aggressive against opponents, and knows better than to take balls away from teammates vs another teammate who is bigger, less skilled, but knocking other kids on their ass, constantly steals the ball away from their own teammates to try to score and impress the coach... Player 1 never even gets to show her aggressiveness because she doesn't stoop to that level and Player 2 makes the team but 2-3 games into the season she's consistently turning the ball over because she won't pass and opponents know to just target her.
Do coaches actually notice that and see the difference to select the "right" player? Or are tryouts intended to just be every boy/girl for himself and soccer IQ goes out the window? Does soccer IQ ever get taken into consideration?
I would not want to make a general statement about coaches in that regard. YMMV