Technology

Ultimately, they can be, but there's lots of differences between them once they reach the bucket you buy. They have different adhesion qualities, but that could be addressed with an appropriate primer. They have different final finish surface requirements, which could be an issue for how the paint works. I remember seeing dragonfly-wing-style paint that was white when viewed perfectly straight buy blue when viewed at any off angle due to a microscopic vertical grid of blue walls. There may also be a required clearcoat component that may not be compatible between the two surfaces. Metal paint is also designed to handle the flex of metal where as concrete paint would barely be concerned about that but possible address crumbling instead.

Edit: and after reading the article, it's a radiative-cooling paint rather than a reflecting coating. Concrete has a much lower thermal conductivity so this may not be effective in transferring heat out of the concrete.