What did the line represent? It’s always surprising how predictable it is to estimate people’s race times given what you know about their fitness. That said, about 10% of the time someone surprises you with a time you wouldn’t expect.
I was working under the hypothesis that my fitness would generally predict my performance when compared to the world record. Turns out for +50% of the worlds top speeds, this works pretty well. New hypothesis would be that specialization occurs way below +50% of the worlds speediest.