For a product that was rushed out to meet a deadline , beating the iPhone 7 launch , could one assume that a risk assessment was made and the cost benefits outweighed the risk at the time.
i see the relation here with the fire extinguisher example. Just going to throw it out there and say the battery chosen was on the cheapest side of the scale, had they chooses the best quality available.... no exploding phones .
Just like the BT module in my Mac Pro , few extra dollars for a better component and I might have a very expansive Mac Pro that works with BT in 2016