[avidiax]

It's true that this method can't say event X was or was not due to condition Y.

But it is fair to say that a pattern of such events that matches (or doesn't) the probabilities given by condition Y is evidence that Y is (or isn't) accurate.

A single heatwave, however anomalous, isn't evidence of anything. Several heatwaves may be ample evidence that one model is more accurate than another.