Can we capture beat to beat intervals in a workout app?

Hi,

I can find no way of getting HKSeriesType.heartbeat() data from the health store using my own workout app. The values captured seem to be from the irregular HRV measurements done by Apple.

There is a video showing HKHeartbeatSeriesSamples being consumed in an app but not how to capture them from the optical sensor.

The WWDC video on this https://stackoverflow.com/questions/77950041/getting-heartbeatseriessamples-in-ios-swift-healthkit-hkanchoredobjectquery at around 28 mins assumes you have written the beats from an external device - not from the optical sensor.

I have set typesToRead to be:

        // Beat addition
        HKSeriesType.heartbeat(),
        HKQuantityType.quantityType(forIdentifier: .heartRateVariabilitySDNN)!,
        
        // end beat addition

Why is the watch app not saving beat to beat interval series to the health store?? Failing that how can the watch app access the data itself so that it can then forward to the companion iPhone app?

Help much appreciated.