This is covered further down in the article where it's pointed out that one of the Merriam-Webster definitions is
>"A usually incongruous mixture : HODGEPODGE"
The author points out that Merriam-Webster actually has a looser definition of salad than they do, because the article is only considering edible things to count.
Also, I disagree - I don't think "fruit salad", or "chicken salad", or "egg salad" etc are "figurative" (not sure what you even mean by that), I would absolutely consider them legitimate salads.
Not saying I agree with the rest of the claims, but it is funny to think of a bowl of skittles as being a salad, and it's always a mindfuck to think about just how impossible it is to categorize every little thing into a neat little box.