That's too dismissive take of the paper. The whole innovation here is the formulation of BaSO4 based acrylic paint that retains most of the reflective properties while being practical as a paint instead of using pure BaSO4 which would be too fragile.

Select quotes:

> Overall, the BaSO4 film reached a solar reflectance of 97.6% and an emissivity of 0.96 in the sky window (Figure 2b). Its solar reflectance is significantly higher than that of the commercial white paint (400 μm thickness), especially in the UV and NIR ranges. [...] For the BaSO4 paint, a standalone paint sample of 400 μm reached similar optical properties (98.1% solar reflectance, 0.95 sky window emissivity)

> To demonstrate the reliability of our BaSO4 paint, we conducted abrasion test, outdoor weathering, and viscosity characterizations. [...] The BaSO4 paint reached a wear index of 150, comparable to the commercial exterior paint with a wear index of 104. The weathering test was conducted by exposing the BaSO4 paint outdoors for 3 weeks (Figure 4b). The solar reflectance remained the same within the experimental uncertainty.