Sprint workouts are a bit different from your typical VO2max short-shorts. They’re supposed to bring you to the point of failure.
See Chad’s replies here: Sprint Interval Training plan?
Also, as he states in the workout description:
The objective with these short, sprint-intensity repeats is to bring about measurable aerobic adaptation in the shortest amount of training time possible.
By repeating efforts performed at maximal intensity, what begin as primarily anaerobic efforts become increasingly aerobically driven.