Which app, and which version? Garmin Connect Mobile app for Windows 10 Mobile? Garmin Connect Mobile app for Android? Garmin Connect Mobile app for iOS? They're all different from each other, so don't presume there's just one app, or that whichever one you're using is what the majority of other users use.
I just checked, and All Day Heart Rate is still there under Health Stats in Garmin Connect Mobile app for Android version 3.7.0.3.