How many people run close to race speed in practice even when going all out?
I know an elite 60m sprinter (6.5mid PB) who has a training best of 6.8mid FAT. Most runs are obviously well slower than that, so I don’t see what the hang up is on doing a good amount of submaximal work to improve speed. Hell, if you look at the Bolt workouts posted and what SF has said, the majority of their “speed work” is in the 90-95% area of their personal best and quite relaxed. That on top of a lot of hard acceleration work, good fitness, and some racing… plenty.