Dealer provided oil change prior to CBS reading

I'm a little confused about the BMW condition based service. When I bought the car - my first BMW, a 2015 320iX, I was shown the car would tell me when service is due and to call when it was nearing 0 miles until service. I had just over 7,000 miles and the car read 1,200 miles until service due - however the dealer where I bought the car called me and said through a computer link-up between the car and the dealer, the dealer was notified an oil change was due. I brought it in and got an oil change under the free maintenance plan along with a free 5 series loaner - pretty nice deal.

What's the deal? Does the CBS mileage on the car mean anything? Is there really a computerized connection between the car and the dealer?

Dealer provided oil change prior to CBS reading