I think when “drinks” are used as a unit, the size varies based on what is being consumed. Like, a bottle of beer, a glass of wine, or a shot glass of whiskey would each be “1 drink”. Again, I could be totally wrong about all this, I don’t drink alcohol.
Did the people reporting their heavy alcohol use know this was the definition it was being judged by, or did they just report the number of drinks they had? I don’t even drink but that seems like a fairly low bar. 2 a day plus one bonus during the week is heavy use? I don’t think many people would agree with that, but I could be wrong.
https://en.wikipedia.org/wiki/Tunica_vaginalis