i am going to put the nonsensical argument aside and focus on the actual question.
this is a fallacy and at best one persons opinion.
first i would want to define "street effective". for this argument i would define it as two guys in a bar who get into a fist fight, the typical dominance thing.
first Okinawan Goju- ryu has weight resistance training incorporated into the curriculum. its not tacked on the begining of the class like doing jumping jacks as a warm up. the weight training is integral to the style. this makes the average practitioner in better shape than average.
second it was never intended to be a sport like main land Japanese Shotokan and other main land styles.
The style has a very grounded stance and composure. this gives the practitioner the ablility and familiarity to standing there trading punches. A bar room fight happens within close proximity, pushing , pulling and trading punches. Goju -ryu is very good at this. Shotokan has become more of a point sparring feel where the practitioner moves in and out of range where the Goju guy is more likely to stand and trade like Wanderlei Silva in MMA.
IF and thats a big IF Goju ryu does have a reputation as being good for street fighting it would be because of these attributes. but i have to add... having a reputation and the actual reality of something are two entirely separate things.