That matches my experience. It basically depends on the glider. To know for sure, you have to get a meter and measure your own canopy.

The problem is measuring. The UV meters I looked at on Amazon just give you a UV index, which will be lower on cloudy days, and higher during the summer on bright sunny days, which means that even though they claim to measure both UVA and UVB, they weigh the UVB much more. You would need to get an expensive meter which gives you the actual data from each part of the spectrum.