But that "article" mainly focuses on lenses that don't block UVA/UVB... there are plenty of cheap sunglasses (most?) out there that are 100% UV blocking or close to it. (Or at least claim to be.)
First, anyone can stick a sticker onto a plastic sunglass, especially if the country you intend to sell in requires a sticker. I don't think US Customs has UVA and UVB, let alone UVC testing facilities, do you? Yes, I know there's still
some ozone in the atmosphere, so, since we're not in AU or NZ, let's ignore UVC for the moment.
Second, the chemistry that absorbs UV on plastic sunglasses is exactly the same as that in sunscreens - and three of the most effective chemical families for
that were recently banned for sale as being carcinogenic. I don't think the Chinese chemical industry has found a cheap replacement for them in less than 5 years, do you?
Thirdly, you scratch the coating and UV protection is gone.
Fourth, if you (read: anyone) have glow-in-the-dark buttons on your remote control, you can test your sunglasses for UVA. Just put the sunglasses over a few of the glow buttons and put them under a strong LED light to pump them. If there is selectivity in how they glow when you turn the light off, you
might have a protective product. It surprised me not one single bit that 3 of my no-name cycling glasses were...crap.
Point being, unless the product is from a name-brand company that can actually be held meaningfully liable under US law, all those UV claims on sunglass stickers are about as reliable as lumen claims on Amazon flashlights. I.E.