Does UPF rated clothing even work??

Does anyone here own it?? Are the one's sold on Amazon even legit? I'm a pale ass ghost living in a hot country and even though I live near the mountains, where it's barely sunny I still get sunburn especially on my back even if I am fully clothed, since winter is here I'm saved from the sun's wrath but I'm looking into UPF clothing. Suncreen is really expensive and tbh it generates a lot of waste I have so many suncreen bottles and tubes that I can't really re-use.