They are "authentic" in the terms that they are produced on Lego molds, but they are not recognized by Lego as authentic figures. They can't be sold on Bricklink as they recognize them as inauthentic. Employees are making them, stealing them, then charging exorbitant fees on eBay for them. A great side hustle.
If you want a bootleg translucent figure you can buy them on aliexpress for like a dollar.