I've noticed the same issue on my 2012 Advance. Prior to the MDX, I had a 2006 Honda Odyssey and had the same issue in the same location. Bottom line, it is poor quality leather in that area, which makes me wonder if it is synthetic or pig leather instead of cow. By the way, I have a 2002 Acura TL with leather seats @ 100,000+ miles and they still look great without the wear patterns the MDX has at only 3,500 miles.
After my Odyssey experience, I've tried to be proactive and clean/condition the MDX seat with Luxor about every 10-14 days. Looks better after I use the Luxor, but only for a while. I've also used mink oil (you can get it at a shoe store) which was recommended to me by the manufacturer of my leather couch I have at home. The couch leather still looks brand new, but it also has top quality (grade A) cow leather.
I'm going to start getting the seat issue documented with the dealer so if it gets worse, I'll have some recourse in the future.