I agree with 99% of what you said here but I think I’d add the caveat that you have to be doing an intra-athlete comparison and it won’t necessarily work comparing one athlete to another. For example, if you took a 9.77 by Powell, Gay, Greene, and Bolt, they’d likely all have differences in touchdowns over the course of the race with Bolt obviously having the fewest. A lot of the variability is simply due to their acceleration mechanics though so I suspect it might be more relevant to look at strides taken from 50m-100m. I would guess that this would more closely correlate with 100m performance.
I agree with your caveat about the touchdowns in the acceleration phase causing the differences between different runners that run about the same times. However an elite 100m sprinter should be taking 46 steps or less in a race to run 10.1x or less. I have to believe Pickering will be the first caucasian to run under 10.00s for 100m if he takes 45-46 steps in a race. Still when you look at all the Europeans who have run the 100m over the last 3 decades you find they have regressed or stagnated in terms of sprint development. I think they have had 6 or 7 on the Continent as whole who have run under 10s and a couple of those guys are ones who changed nationalities and didn’t officially run under a national coach or national HP program. The European programs seemed to be geared heavily on stride rate improvement which I think comes from their track cycling backgrounds which pedal rate and for good reasons is a major factor for speed in track cycling events because they can only use 1 gear. The giants in Sport Science in Western Europe come from the British, the Dutch, the Italians, and the Fins. A ton of old Eastern European literature exists now, but they are no longer what they used to be with exception to Coh.