It's literally a dichotomy by definition. If I say "in a comparison between chocolate and vanilla" I'm literally comparing those two specific flavors. To tell me it's a false dichotomy is silly.
I guess they are saying that there are other options. So for example if I asked you "what is your favorite ice cream flavor, vanilla or chocolate?" you might respond to me with "that's a false dichotomy, there are more than two ice cream flavors, my favorite is banana which you have not listed as an option". At least that is my understanding of the context.