It's a 19 year old without a college degree, I think it's a reasonable criticism.
If the study uses non-factual information or does not interpret the data by understanding the nuances that may yield different interpretations, then the author's educational background may offer an explanation. But that isn't the critique here.
It's just reverse ageism with a mix of elitism.
Studies stand or fall on their own merits. The background of the author isn't actually relevant to that. If the study holds, it holds. If it doesn't, it doesn't.