If you clench any material for an extended time it will act like brace and move the teeth. Clay is abrasive. But even a soft rubber bit will move teeth if you clench for hours. If you don't clench then not so much.
I find Jolly Ranchers to be worse. I can’t tell you how many fillings and caps I pulled off w/this candy, but they’re gooooood. I find acrylic to be harder, but I typically don’t clench, so it’s not an issue.