this has more to do with the way we stereotype or funnel athletes than reality. the trope is you turn a fast football player into a sprinter or hurdler. they rarely do 800 or mile. guy i ran sprint and mile relay with junior high was the tailback then. went to HS, dropped football, became an 800 guy, made state. we reflexively label such players fast twitch and herd them to relay distances.
i also think you're missing that, a) TF-dedicated people running the quarter or 800 are often pretty darned good short sprinters who are merely specializing where their bread is best buttered; b) a sub 44 quarter guy is averaging splits under 11, and c) conversely tyreek hill proved a so-so 100m guy.
i personally think if you took untrained but professional football skill players and then world class 400/800 guys they actually might have similar fitness and speed -- the football guys need to be fit to do play after play -- but it would probably favor the track people. track speed is different than speed in other sports. i thought this trope already got blasted.