Unless you have access to the research, stop making conjectures on information you don’t have. I can’t provide books for you for free so you need to pony up and catch up with sprinting data.
Second, so why are people improving? The suggestions you had are nutrition (chicken nuggets), training (using 1968 training models), and equipment (what evidence). Nothing that spells 2011 Star61. Like I said earlier, people are stringing together better splits but bolt didn’t hit a 1.62 for the first 10m and his top split was a factor of his height and limb length, not his squat strength! Accept the facts no holy grail exists.