Err, actually, yes it is. The frequentist interpretation of probability makes the claim that probability theory can only be used in situations involving large numbers of repeatable trials, or selection from a large population.

Depends which frequentist you ask. From Aris Spanos's "A frequentist interpretation of probability for model-based inductive inference":

It is argued that the proposed frequentist interpretation, not only achieves this objective, but contrary to the conventional wisdom, the charges of ‘circularity’, its inability to assign probabilities to ‘single events’, and its reliance on ‘random samples’ are shown to be unfounded.

and

The error statistical perspective identifies the probability of an event A—viewed in the context of a statistical model Mθ(x), x∈R^n_X—with the limit of its relative frequency of occurrence by invoking the SLLN. This frequentist interpretation is defended against the charges of [i] ‘circularity’ and [ii] inability to assign ‘single event’ probabilities, by showing that in model-based induction the defining characteristic of the long-run metaphor is neither its temporal nor its physical dimension, but its repeatability (in principle) which renders it operational in practice.