I wasn't meaning to argue anything beyond perhaps bringing to light how naïve these studies are. We don't count alcohol consumption this way. Is someone that smokes once per week for 20 years a heavy user? Would anyone consider someone that drinks once per week for 20 years a heavy drinker?

Why do these studies assume weed is cumulative but alcohol isn’t? Is it because most researchers have experience with being drunk but zero to little experience with being high on weed?

It seems likely there is a difference between someone who is buzzed all day every day for years vs someone that smokes several times each weekend, but these studies all group them together as one. Most likely because the researchers don't understand what they are studying and produce results that do not match the lived experience of their research subjects.