Again, if it came on and the dealer didn't do anyting about it, or reset without doing the oil change, then it's on them, especially since they were specifically asked about it, apparently.
On my car, it came on in yellow and I scheduled it for it's oil change thinking that's what it was for. The dealer hooked up the key fob and it said it was ready for it's 6k inspection, but it still was not ready for it's oil change. For the warranty and free maintenance, they will do it when the car tells them it's ready, not before. If something happens, it's on MINI.