Alcohol being harmful no matter the age (and most importantly in this study, no matter the quantity) does not mean that it is equally harmful at every age and every quantity.
The study your link is referring to talks about alcohol being a vector for cancer and other health problem at an older age, and disproving the myth along which low alcohol consumption would be good for the heart. It did not take into consideration the age where people started drinking.
Alcohol being harmful no matter the age (and most importantly in this study, no matter the quantity) does not mean that it is equally harmful at every age and every quantity.
The study your link is referring to talks about alcohol being a vector for cancer and other health problem at an older age, and disproving the myth along which low alcohol consumption would be good for the heart. It did not take into consideration the age where people started drinking.