I believe Note 7's battery do have design problem and some phones genuinely caught fire, but the issue might had been blown up much bigger than it really was such that it did not give Samsung chance to investigate and confirm the cause, affected batch etc.
It was mentioned there are 90+ reported cases. How many phones out of these reported cases are returned for investigation. I can similarly puncture my phone battery, let it catch fire and just post some pics online. It will be reported by all the media within hours and none of them will bother to find out if it's real.