Thanks for sharing! I was always wondering how climate scientists were able to identify if an event was due to climate change. Now I have a good reference!
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.