Would indeed be great if they did that, but unfortunately, that's not how Apple has set this up. If you are wearing an Apple Watch and the Airpods Pro, the system defaults to the watch and ignores the heart rate data from the airpods. This is how it works with the Powerbeats, which also have heart rate monitoring.I think if you’re using both an Apple Watch and AirPods, it should be possible to get a more accurate heart rate. With two sources of data, the device could provide a more precise reading, which would also improve the accuracy of calorie tracking. I don’t think the system would rely on just one or the other.