I have read many disclaimers. They are required so that the product does not come under FDA cognizance for making medicinal claims for a dietary supplement. If we did not have that unconstitutional FDA, such claims could be made and tested for veracity. Yet another "solution" from FedGov that creates many more problems than it could ever resolve.
They could be tested for varacity by someone other than the FDA, UL could do it as you suggested. Instead the suppliment industry remains almost entirely untested by anybody, including the companies. Disclaimers are used throughout advertising to undo promises, not just in the suppliment industry, the most famous disclaimer in history has become it's own meme: your milage may vary. That's how promises get unmade in the world of selling things to people, unmaking promises is how you avoid fraud suits. I'm not saying there needs to be a government solution for this, I'm just saying that anytime you think a fraud suit can stop a scam you need to look for the disclaimer, if there is one then no a fraud suit cannot stop that particular scam.