Fairly common. I have similar scratches in the same place on mine. To help eliminate the friction and hitch sounds, smear the ball with a good coating of bearing grease. Every 1000 miles or so I wipe it off and apply fresh grease. Between trips I found a 9 oz Solo cup fits perfectly on the ball, stays securely even while driving down the Interstate.
I used lithium grease when I had a TT but I have read where other people use wax paper for lubrication. If wax paper works it would be a lot cleaner then grease. They do sell Teflon grease for the ball. Reese used to sell one as well.
2011 Dodge 3500 DRW CC
2015 Open Range JT337RLS
Normal for a chrome plated ball.....I've used both chrome plated and non-plated 2" balls. My 2" non-plated ball is smooth as silk while my chrome plated ball looks just like yours. My theory is that the chrome plating acts like a coarse abrasive as it first chips and peels off.