These are konjac-based. Fwiw, such a thing might conceivably exist, but I've never heard of shirataki made from true "yams" (though there is a version made from tofu). Konjac is often referred to as a sort of "yam" in English, but strictly/technically it's not actually related to plants that are "scientifically" considered to be the "true" yams at all. In that sense, it's kind of like we Americans referring to sweet potatoes as "yams", even though they're also not even remotely related to the food plants that produce "real" yams...
I am relying on memory, as my noodles are long gone, but I believe this brnad is made from konjac flour. The ones with konjac flour are literally carb and calorieless, while the ones made with yam or soy have some calories.
Konjac flour noodles come in several varieties made from the root of the konnyaku imo plant (Konjac plant or elephant yam), which is a wild-yam like plant native to Asia. The flour from the plant is called konjac flour. Konjac root is composed of water and glucomannan fiber. It can be ground into flour, boiled and shaped into a substitute for pasta or rice noodles. The Japanese traditionally make konnyaku or shirataki noodles by mixing konjac flour with water and limewater (calcium hydroxide).