I think the base athleticism is the same. I think the knowledge about nutrition, training and conditioning and injury care are far superior and that's where the difference lies...
Some of that is definitely the case, but he highlights how just changing the material the track is made of makes almost all the difference between Owens and Bolt. He makes this point again by showing the technology in bathing suits with Olympic swimmers.
The technology of equipment, facilities, etc. has exploded and enabled elite athletes to maximize their efforts.
The 2nd major area is the specialization of athletes that we now do. Back in 30s-50s, it was about being competitive at multiple sports/positions. An average body type. Today the elite athletes are selected and sorted based on ideal genetic makeups ... a WR could never be a LT in the NFL.
This was further shown with that crazy height statistic -- if you know a male in 20s-30s above a certain height in the US, they are practically guaranteed to be in the NBA right now. But height isn't the only thing NBA looks for, the average NBA player also shatters the conventional rules about limb:torso ratio. Da Vinci's human circle doesn't work for NBA players.
He made it again with the Kenyan runners - the most elite distance runners in the world are Kenyan, but even among Kenyans they come from just 1 tribe that has those crazy genetics of long limbs and short torsos.
It's the Horses of Courses principle applied to pro athletes.