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.

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.

The world record is not 1 data point, it is a property of all human running in history.