Yes, it’s true that it hasn’t been thoroughly determined how blending insoluble fiber affects digestion, and Lustig is exaggerating–what he claims is more thoroughly shown with grains. The purpose of that article was just to give an overview of some of the issues with regard to glycemic load and response—the fact that the author herself did some bogus detox is irrelevant, because the issues themselves have been addressed by legitimate studies e.g, the Lancet study, Bolten, Flood-Obbagy & Rolls). There has been enough serious research showing that whole fruit vs. blending can affect glycemic load and satiety that it shouldn’t be simply brushed off as “woo,” (and Stark’s blanket statement doesn’t really address this particular issue).
And really, I would say that it may be not even be necessarily “bad for you,” as Quartz said, that you digest sugars differently with blended food—just that there is evidence to show that blending can change how it’s digested. I think the most recent research seems to indicate that different fruits are affected differently, and that blending vegetables might even be better.