Yes, just about any visor these days block out UV rays. It is the reason I don't bother with photochromatic eyewear any more. Sun's UV rays are what trigger their color change, and behind the visor they just don't change color. Same as with the windshield and side windows of cars/trucks/SUVs these days. They all block UV rays.
You might still feel the heat when the sun hits you through them, but that's carried by IR part of the light spectrum, not UV.
Personally, I hate those drop downs. They never come down far enough, and they don't stop the sun from heating up the inside of my helmet like a middle school science project.internal sun shade are the way of the future. Period. And once you get used to it, tinted shields become instantly obsolete.
Personally, I hate those drop downs. They never come down far enough, and they don't stop the sun from heating up the inside of my helmet like a middle school science project.