Genuinely curious but how is this > "the current rate of extinction is 10 to 100 times higher than in any of the previous mass extinctions in the history of Ea

Genuinely curious but how is this > "the current rate of extinction is 10 to 100 times higher than in any of the previous mass extinctions in the history of Earth." an accurate statement when there have been a few mass extinction events that were (apparently) caused by sudden changes? Is this assuming that the Triassic-Jurassic extinction event was caused by gradual changes instead of an impact or volcanic event? Same for the Cretaceous–Tertiary (K–T) extinction? I think there are also a number of extinction pulses in the record that could be attributed to sudden events although I'm unsure of how they compare in terms of the number of species affected.