It is better to be safe than sorry with you bird's life. Sandpaper covered perches are not good at all, they can cause foot problems. I would never let one of my birds have one. If you buy a cage with a sandpaper perch toss it out. Replace it with a mineral one, they work better anyway.
Perches now come in many different shapes, sizes, types, and textures.
It is not uncommon to see cactus wood, plastic, and other types of perches. Make sure the perch is not slick, and the bird can have a good grip on it. Also, replace all perches once they become chewed.