I found this on WorthPoint from a seller: Even though La Tausca was know for faux pearls, at some point they merged with Heller-Deltah who then sold cultured pearls under the La Tausca name.
In the ads for La Tausca imitation pearls they're described as "simulated." Even in the ads from the early 1900s, when advertisers could get away with calling a bead a pearl, they used the common term for fakes - "indestructible pearls." It doesn't seem like the company would call the same pearls "imitation" in one place and "cultured" in another. Still, your certificate says they're cultured pearls and I think you have to leave room for that possibility. My first reaction was La Tausca = simulated and a Google search showed mostly the same thing.