2003 Wrangler X Brake Shoes

I bought new rear shoes for my friend's 03 Wrangler X. The new ones have a flat, level surface, but the old ones have a groove through the middle on both sides (its the same thickness on both sides, like it was made that way), kind of like there are two shoe surfaces in one. I can't seem to find any info. Are the shoes supposed to be grooved? I can't seem to find any grooved shoes on any parts store's websites, and they're closed so I can't go ask. Does anyone know?

The factory shoes may have the groove as a noise suppression thing. Our 04 Wrangler has grooved ones also.