I ran with a friend this weekend, and we both have the Forerunner 235. The difference is that I have a Samsung Galaxy S6 and he has an iPhone. He noticed for this first time that his "My Day" summary page showed a heart rate graph, similar to the daily on in the heart rate section, that is located under the 'active calories' and 'activities'. Is this only for the iOS version of the app?
Today the mobile app for Android displayed an invitation to join beta program for the "My Day" screen. I declined, but the description of the beta version indicated some significant changes upcoming for the "My Day" screen. Perhaps your friend with the iPhone is running a beta version or perhaps the new version is already deployed for iPhone but still beta on Android.