I’m not saying you’re wrong about your greenhouse, but I wonder if you aren’t misinterpreting the manufacturer’s info. Greenhouse plastics are almost always UV stabilized, but not UV filtering. The light transmission is a separate rating, and doesn’t necessarily mean it filters all spectrums of light to the same degree. In my experience, double-walled corrugated polycarbonate panels have a wide range of filtering/shade options, while hoop house poly tends to just affect light transmission without much UV filtering.
UV stability just means the plastic won’t become brittle and degrade after a few months of summer sun, which is exactly what happens when you try to use poly tarps meant for painting.