Just wanted to jump in here and say that I, too experienced the same issue with the Logitech keyboard - and it was because of this thread that the Apple Store that I went to had zero problems immediately replacing my iPad and keyboard (currently typing on the iPad Pro smart keyboard).
Some small details: I purchased my iPad Pro on Jan 27 2006 and on the suggestion of the salesperson at the Apple Store, bought the Logitech keyboard instead of the IPad keyboard - he suggested it would protect the back and front of the iPad as well as offering more stability when I wanted to use it in bed or on my lap. I have to admit - I really did love the keyboard - until this month when I noticed the same lines that I saw in the photos above. At first, I too thought that I would be able to remove them, but when they were readilly apparent during a presentation I was giving (On March 22nd) and then I really made an effort to remove the scratches and realized that they were damage caused by the keyboard, I took to this forum and found that the sad reality was true.
Yesterday I returned to the Apple Store where I purchased the iPad and showed a repair person the keyboard and linked to this forum. He was fantastic. After going through the motions of also trying to wipe off the scratches, he immediately set me up with a new iPad, and I paid the difference for the new keyboard.
I should also mention that don't typically carry this iPad around in a bag where it can get compressed by other things. I usually carry it in a sleeve and put it in my purse - so it's not likely any undue compression caused this. Just think the simple act of closing and opening it over time caused it. Bums me out too, because I actually really liked the keyboard.
I'm hoping that Apple realizes that this is an issue and stops selling the keyboard. And hope that Logitech pulls the keyboard until they can resolve the problem.
Hoping others find this forum - and find other Apple reps that were as friendly as mine and are just as eager to help find a solution to this problem if you find yourself having it.
Good luck!