Ok, quoth Oxford:

> the use of humor, irony, exaggeration, or ridicule to expose and criticize people's stupidity or vices, particularly in the context of contemporary politics and other topical issues.

In this case, they're using an analysis which is commonly used to "show activity" in various psychological and psychiatric contexts to "show activity" in a dead salmon. This directly exaggerates ("truth, but in the most extreme way" is about exaggeration, in my definition) and shows the futility of trying to draw significant results without screening for random chance among thousands of comparisons.

A comparison I'd make is to arch-satirist Jonathan Swift's "modest proposal" - it described a real problem (i.e. famine in Ireland) and skewered by exaggeration the English tendency to prescribe solutions that affected none of the core issues as though they knew best and could overcome English exploitation, greed, and callous disregard by the right public policy.