I someone dragging a wedding ring (or other) by chance? That's the only time I've seen that--especially rings with strong (closer to right angle) edges.
I would go back and grump at the dealer--not normal unless there's a ring really gouging it. I treat my steering wheel with 1Z Lederpflege 2x a month. I'd say that's not normal.
Get a new wheel--good luck! I would be in the dealer as well. I have a passenger bolster on the seat wearing too fast--so I understand where you're coming from. And the seats are treated at least 1x a month.
12 550xi Dark Graphite Metallic II. Convenience, Cold, Driver's Assistance, Premium Sound, Sport, BMW Apps