Having a 100% endurance response is rare but by no means impossible; about 1% of individuals come back with it.
With the power/endurance response, what we are looking at is how well someone responds to power or endurance based training - not how good they are at each element. It essentially provides some insight into how to set up a training programme. We would class endurance as volume based training, and as such we would predict that those with a heavy entrance bias would respond better to higher volume training. In the gym, this would mean moderate weight and higher reps, such as 3 x 15 reps.
It is also important to take into account the goals of the athlete. If for example the Athlete was training to be an Olympic Weightlifter, then 3 x 15 reps would not be appropriate. In this case, “volume” based training would still be higher reps, than power (intensity) based training, but 5 sets of 4 reps might be more appropriate.