I don't think it faulty in the sense that a plastic or metal part might be. Leather is a natural product and there's always some variation, but that's something you might take up directly with Brooks.

My (not Brooks) leather covered saddle on the commuter has similar wear/damage in the back. The center is high polished from cycling shorts, but the rear beyond where my weight is is rough. I believe it's from grit thrown up by my rear wheel roughened it with incidental pressure like from when I'd shift my weight.

If I were you, I'd call Brooks, and ask them if they feel this is normal, or your fault, and how best to deal with it.

BTW- don't over use the Proofhide. It softens and relaxes the leather, and if used excessively will cause the saddle to sag prematurely. My 45 year old Brooks Pro is still going strong after over 50,000 miles (though I don't ride that bike as much anymore). I was very sparing with leather treatments, so the leather kept it's shape nicely. I used neatsfoot oil early on until it was broken in, and thereafter only treated the top with saddle soap and polishes I bought at an equestrian store. In all that time and mileage the only thing that broke is the frame in the back, which I had a friend weld back together.