Here's an actual explanation of the 'sneaked reference':
However, we found through a chance encounter that some unscrupulous actors have added extra references, invisible in the text but present in the articles’ metadata, when they submitted the articles to scientific databases. The result? Citation counts for certain researchers or journals have skyrocketed, even though these references were not cited by the authors in their articles.
What they see as "bad research" is looking at an older cohort without taking into consideration their earlier drinking habits - that is, were they previously alcoholics or did they generally have other problems with their health?
If you don't correct for these things, you might find that people who are not drinking seems less healthy than people who are. BUT, that's not because they're not drinking, it's just because of their preexisting conditions. Their peers who are drinking a little bit tend to not have these preexisting conditions (on average)