Do suction-cup tub mats work on textured or stone tubs?

No, and reviewers are blunt about this. The New York Times specifically flags that the Gorilla Grip patented mat's suction cups 'don't work on textured or tiled surfaces,' and r/bathrooms users complaining that mats 'never suction to the bathtub floor' almost always have textured tubs. Suction mats are only reliable on smooth, glossy acrylic or porcelain.