According to all available information, Samsung have determined that it ONLY happens during charging. It doesn't just " catch fire in someones pocket" (as I Phones have been known to) So asking you to just switch it off right now is just the typical response to modern risk management. Or the Elimination option of the Risk Management Hierarchy of Control, I suppose. These have been an exceptionally popular new release, majority of reviews rate it as the best Android phone currently available. So hundreds of thousands out there in the first few weeks. Battery fires (not explosions) during charging happened in some tens of cases. (initial report was 35 worldwide, two in Australia) Telstra were straight onto it, I registered and there is a loan phone on its way to me with a return mail bag for the GN7 . Which doubtless means that my "dangerous" phone, as well as thousands of others, will be in freight holds of aircraft in the coming weeks.
Irony, much?
BTW, I have always been slightly uncomfortable with leaving anything with a lithium battery on charge and unattended. It has long been my personal practice to have such things as phones and tablets charging on a non-flammable surface such as a stone benchtop or sink, wherever possible. So for this phone, ops normal until the replacement arrives.