I don't disagree that the relationship of wine to grapes is an important one, but we were just talking about a very generic scale.
One side of my scale was
"Side B: wine is distinct from other alcoholic beverages; it may have other active ingredients and should possibly be studied for beneficial effects of intake as well"
How is it distinct? It comes from grapes. What other active ingredients? Grape compounds.
So the scale still had containers to insert the specific detail of grapes.
To put grapes ON the scale means that someone in the passage took a contrary opinion towards grapes. That's a bit of a stretch.
But really, I'm not disagreeing. This is just the silly game of words you can get into when you're trying to come up with "the perfect scale". The scale is just an approximation - a useful tool for organizing info in the passage. There's no one correct version of it, so if you have a suggestion for how to word it, using 'grapes', please suggest one.
I honestly don't really try to impose a scale on a passage like this. Obviously, the author is trying to clarify a misconception or point to a deficiency in research, so we could define an opposing side based on the misconception or the overlooked research opportunity, but it's not like that side of the scale gets any talking points.
It's MOST important that we know what missing idea the author is trying to supply to remedy the misconception or address the deficiency, and in this passage that idea is clearly "wine is special among alcoholic drinks because its grape compounds do some cool stuff for heart health".
This discussion is making me really want some red wine.