How self-referentially absurd. More precisely, epidemiologists do this day in day out using biostatistical models, then applying causal inference (the counterfactual knowledge part incl.). I said biostatisticians because epidemiology isn't in the common vernacular. Ironically, counterfactual knowledge is, to those familiar with the distinction, distinctly removed from the biostatistical domain.

Just for the sake of intellectual curiosity, I wonder what kind of paradox was just invoked prior to this clarification.

It wouldn't be the epimenides paradox since that refers to an individual making a self-referentially absurd claim:

The Epimenides paradox is the same principle as psychologists and sceptics using arguments from psychology claiming humans to be unreliable. The paradox comes from the fact that the psychologists and sceptics are human themselves, meaning that they state themselves to be unreliable

Anyone?