It's a good bit of reading although I'm not sure I agree with all of it, well mainly where it says,
"similar height, similar roof-lines, similar stance, similar-looking bonnets, windscreens, B-pillars..."
Now I have one of each and park my 172 right alongside my other half's 133. The 172 is noticeably lower, in terms of how you get into the car and looking at the roofline side by side, a good few inches different. The 133 is taller in stance on it's bigger wheels the 172 looks more low slung and in turn looks longer, even if it's not.
I get the impression they mistake the fact that it is a Renault with the fact that the Twingo is based on the Clio MKII and that by default it will have similarities. In the same sense I can climb into a Clio 197/200 and see similarities with my Megane.
I guess I just mean that as much as they share the same platform and are equally fun for different reasons, they're not as similar in my opinion as they let on in that article.