Ive never read about anyone who just use uvb producing bulbs to grow with , but I have read reports and forums about people who have used uvb bulbs during flowering as a source of uvb . The therory is that uvb light (the same kinda light that causes suburns in humans) causes the plant to produce more tricomes to act as a sorta plant sunscreen against the uvb light. Which makes the plants more potent. There is actaully some evidence that this could be true
studies where areas of high uvb light have had more thc content in the cannabis. Im actually considering adding two 48" 7% uvb producing floros to my grow during flower. Just my 2-cent.