Hi, thank you for posting photos. I have not seen this on my bag, only the wavy effect by the magnet. Also a little wavy on the top right of the flap.
Your back doesnt look bad at honestly. Do you keep something in the little slip pocket?
I used to keep a small compact in the slip pocket but I stopped when I saw that forming. It seems to be getting worse tho :/ I guess I'll have to keep an eye on it.