To be clear, the study actually does not show any statistically significant effect of exercise on mortality rate compared to the control group (it shows an improvement, it's just not statistically significant).

The verbatim conclusion they present is:

"This study suggests that combined MICT and HIIT has no effect on all cause mortality compared with recommended physical activity levels. However, we observed a lower all cause mortality trend after HIIT compared with controls and MICT."