The whole UVB thing with frogs is just another stress to the hobbyist, so much conflicting information takes the fun out of enjoying animals as you're more concerned on the set up rather than the frog itself. Many people come out with broad statements that seem more a personal opinion rather than fact. I don't think there's been enough evidence to actually support that frogs actually need it but there's evidence that they've been kept and raised without for ages and just provided the correct dietary supplementation instead. I encourage more research be done but IMO it's too early to say that all need it, if they did then there would be more sources to say that they did.