What I see in that graph's purple line is that with the most basic concurrency you can have that is not nil, you get better times than some statistically optima

What I see in that graph's purple line is that with the most basic concurrency you can have that is not nil, you get better times than some statistically optimal load-distributing solution (choice of two). I'd like to see similar graphs with 4, 8, or more workers to compare them.