The IFR is different for age-stratified groups. The IFR was calculated before COVID-19 vaccination became widely available.
It's a big deal because it reports a markedly lower COVID-19 IFR than previous studies. The panic may not have been warranted for non-elderly age groups. I read this to also mean that the risks to adolescents did not warrant school closures and for some ages vaccination, even though vaccination risks for this age group were minimal.
"...in many locations excessive hospitalizations may have been driven by irrationally high perceptions of IFR for non-elderly people and they may have caused unnecessary stress and damage to the health care system at large."