How would you define “fitness”? Imo, fitness is the readiness for perform a specific (physical) task.
Does sprinting require fitness? Yes.
Does sprinting require the type of fitness to run a 1500m race or compete in an amateur boxing contest? No.
This kind of mentality that sprinters need to build a big fitness base was held years ago by the coaches who had their sprinters run long distance in the off season. Of course that was bs, just like long ass speedball workouts is bs!