In regards to track surfaces and “what could have been done on today’s surfaces” let’s not forget about who may have been the fastest sprinter of all time: Bob Hayes
As to the question of sprint mechanics, there’s no question, in my view, that not only must the dynamics be individualized in order to suit each sprinter’s anthropometric proportions; but also their output potential at any given time (which obviously develops up to their peak)
I still think it’s fascinating that Nesta Carter essentially goes into complete knee extension prior to ground contact; hence, obviating “stepping down”. Something that Mo Greene also seemed to do which is really pronounced on the 6.39 in which he jumped but didn’t get called.