It's the scalability of these things that means they never leave the lab.
Can't imagine Dulux will be able to start cranking out 40l tins of the stuff. Also, does it stand up to the elements? How often does it need replacing? What energy / climate cost is there to manufacture it?
Just paint your roof white people!
https://www.positive.news/environment/climate-crisis-white-paint-more-effective-than-air-conditioning/
Would interesting to see real world performance over their make believe calculations.