Being frank, some of the discussions on FB suffer from being ill-informed. Too many opinions on every topic, most of them wrong/clueless IMO!
The last photo above of the right side shows it best; the arches have a “bias” in their shape, with a high point that should be towards the front of the arch, along with the widest point, that should tail off afterwards. In the photo, the high point of the flare is around the fastener underneath the quarter vent /emblem; that’s wrong, as it should be around the faster to the right. It leads to the slimmer, tailed off part being around the front of the arch, and it being too short-looking at the back and too high.
Here’s a pic of one on my project car:
See how the widest portion is around the third fastener from the front, and then it tails off on width after that?