We can’t infer much about how fast others run. Only that it’s possible to run 100m in 9.81s. We don’t know if everyone else can do that, or no one.
Yes we do, we know it's the world record. That's the data point.
I would not call it "powerful" that you can infer from "X is the world record" that "nobody is faster than X".
It's not even inference, it's simply saying the same thing in different ways.
And in any case, it's of course not very relevant for his main argument anyway, since don't don't have any such data-points about aliens.
If we knew that "humans are the smallest intelligent beings in the universe" well then yes could "infer" that all aliens are larger. But that is trivial and pointless.
What if you knew instead that one particular human being can run 100m in 16s?