so you have no reason to conclude that their X-skill is normal for any arbitrary X
I mean, you have some priors, and priors are a totally valid thing to reason from even if you’re not taking a uniform random sample of all people.
In general, “I have a few samples of X, and I don’t have any particular reason to think they’re unusual samples, so on priors they’re probably typical” is a totally valid way to reason even if your samples aren’t uniform random from the population.
I mean, you have some priors, and priors are a totally valid thing to reason from even if you’re not taking a uniform random sample of all people.
In general, “I have a few samples of X, and I don’t have any particular reason to think they’re unusual samples, so on priors they’re probably typical” is a totally valid way to reason even if your samples aren’t uniform random from the population.