Just replaced my series 3 with a series 4 sport gps, as well as my iPhone 6S plus with an iPhone XS. Both devices were setup as new, without restoring any old data. As I'm not allowed to wear the watch at work (I work in a hospital), I keep it locked in my desk drawer during work hours.
What I've noticed is that the watch seems to report regular heart rate readings to the Health app even when it's just sitting idle in the drawer. I first thought it might have to do with the "unlock with iPhone" feature, as I regularly use my phone while in the office. But I can't really find any noticable pattern there, so I'm not sure. Anyone else experience this behaviour? The HR sensor seems to work fine and report precise readings while wearing the watch, so guess it's software related somehow.
What I've noticed is that the watch seems to report regular heart rate readings to the Health app even when it's just sitting idle in the drawer. I first thought it might have to do with the "unlock with iPhone" feature, as I regularly use my phone while in the office. But I can't really find any noticable pattern there, so I'm not sure. Anyone else experience this behaviour? The HR sensor seems to work fine and report precise readings while wearing the watch, so guess it's software related somehow.