I tend to agree with this. This is why Bruce was so stuck on being in the best shape possible. He always stated that if you are not in shape you cannot win in combat. He also beleived in a strong core and forearms. He spent hours on his forearms alone.The effectiveness of a Martial Artist is based on the skill and ability of the individual Martial Artist. No system be it SD or Sport will beat big strong, quick, athletic and skilled.
This is even more true in the so called "streets". Unless you are Bruce Lee. Bigger, stronger, faster wins more times than not! The superior athlete wins most of the time! If they have the nerve to fight.