Inside of my BACK tires worn to cords outside fine WTF

This one is new to me. Have a set of Hoosier QTP's on 15x10 welds on the back of my Camaro and just happened to notice the inner 1/4 of tread is down to cords while the rest of the tire is in great shape 1/2 to 3/4 of tread remaining. I've seen this on fronts due to alignment/ worn suspension issues , but never on the back tires of a solid rear axle car. Why did this happen???

they could be rubbing SOMETHING back there just enough to do the damage, but not notice when driving

rubbing imo