Has nobody considered the possibility of such vast, shiny external reflector walls absolutely, very literally roasting the surrounding landscape when struck by the already ferocious Arabian sun? How would a person even survive openly coming close to this fascinating monstrosity from either side at certain times of the day? I remember a story about sunlight reflections bouncing from the "Walkie Talkie" Building in London to then scorch some poor fellow's car in the streets below at certain times of day in the summer. NEOM strikes me as a would-be case of this on a truly infernal scale.
You are missing the central point of the Walkie-Talkie and Disney-Concert-Hall controversies. These are Frank-Gehry(-style) buildings, and in those roughly half of all surfaces is a concave and half is a convex mirror. THIS concentration to one point is what turns the summer sun into death rays.
Reflected sun, by definition, has a little less energy than direct sun. So, given the mirror walls are straight, as the designs show, you get (at maximum) 200% of normal desert sun energy, which isn't comfortable, but not a Gehry-style death ray.
You're grossly understating just how brutal it would be. While you're right about how concave mirror surfaces truly create lethal concentrations of energy, this vast reflective surface would still unbearably heat the land next to it at certain times of day. 200% of Arabian Peninsula levels of solar heat as only "uncomfortable"? You've got to be kidding.
