I did find this from the NIH on UV-B light:
Cannabis Inflorescence Yield and Cannabinoid Concentration Are Not Increased With Exposure to Short-Wavelength Ultraviolet-B Radiation
Before ultraviolet (UV) radiation can be used as a horticultural management tool in commercial Cannabis sativa (cannabis) production, the effects of UV on cannabis should be vetted scientifically. In this study we investigated the effects of UV exposure ...
www.ncbi.nlm.nih.gov
which backs up what you heard.
But they did hit it with so much UV-B it created changes in plant growth, so I wouldn't say it's definitive.