No Live HR in Garmin Connect "At a Glance" w/Watch Powered On Nearby

Garmin Connect does not show "live" Heart Rate from the Index Sleep Monitor in the "At a Glance" tile while my watch is off my wrist but still powered on and connected to my phone.

HR data is shown immediately after powering off the watch. Powering the watch back on results in "- -" being shown.

Garmin Connect iOS version 5.16.0.35

ISM software version 3.70

Fenix 6X software version 28.02