I think it's in quotes because prime numbers have a probability distribution, but it's (obviously) not a uniform distribution. I think that the article is trying to say that there are more subtle rules around the distribution than just probability density.

By "probability density", I mean that the probability of a number around n being prime are about 1/ln(n) -- see the Prime Number Theorem[1] for more -- but of course any given integer is either prime or not.

[1] https://en.wikipedia.org/wiki/Prime_number_theorem