there are lots of video in YouTube related to this as people over hyped it by naming it fake camera,
however the thing is in each and every phone who has telephoto camera works like that only, it depends on the environment colour if it's white or not that much dark then phone uses the telephoto camera itself but in dark place of dark objects or dark colours & dark environment (here dark means darkness in any colour) it automatically detects and uses the main camera to give you better shots because telephoto couldn't do that in that condition or context, that's how triple camera management works in each & every phone to give you better shots. if you check in OP7 pro too, it'll work the same ..... depends on what colour content you are representing the camera.
thanks :)

I covered the telephoto lens in day light then also it uses the Main camera.