You're forgetting to take into account how deep the prints are, how weather changes affect the fossilization process, weather like wind, and many other things that you can't tell by a simple picture that they use to accurately indicate what happened there.
I agree that there are variables and i'd love to read a full report on the findings. I think it's likely that the speedsters footprints aren't the same ones seen in that photo. I find it highly unlikely that any fossilized footprints that are currently spaced 18" apart could have been made by a human running faster than Usain Bolt.
I'll take one whole women plz