What does the layered HDR icon mean in my photos? I have the iPhone Xs and I’m interested in the Smart HDR feature. I note that it is enabled by default. However, only a handful of the photos that I have taken over the past week or two have the HDR icon. If I disable Smart HDR and take a photo before and after manually activating HDR I don’t get the icon overplayed on the resulting photo. It definitely looks like the HDR is working but I just don’t understand what the icon means.
Older iPhones would put the 'HDR' overlay only on pictures that used HDR.

The iPhone XS/XS Max has some form of Smart HDR on at all times (when turned on in Settings).  You will only see the HDR overlay for times when the system had to use extreme or excessive HDR to the photo.

If you have Auto HDR turned on then be assured that it's apply Smart HDR to your pictures.