Kind of funny, our company is on the cutting edge actually, but in fluorescents, not LEDs, which are terrible for producing what we would consider high output of UVB or UVA. There is a huge difference between 320nm and 399nm, yet both are "UVA". 320nm has a lot more energy, and as you up in frequency (down in nm), it forms a Bell curve and gets exponentially more damaging. It also goes down in penetration, which is why you can get a quick flash burn from UVC (100nm-280nm) that doesn't penetrate more than a few layers of skin, but it is very damaging to those layers. And of course, the real kicker is how much you are getting.
And the reason it has that warning on it is simple: anything with any measurable amount of UVA must have that warning by law. The FDA regulates this (CFR 1040.20 for sunlamps, for example). I'm used to seeing them regularly for inspections. For some reason, general lighting fluorescents are excepted from this warning, even though they do produce a measurable amount of UVA.