There was a lot of smoke related to Bottas possible jump starting the race. Many felt his reaction was super-human and impossible.
Right at the start of the race Vettel reported that Valtteri Bottas jump started the race and that it should be investigated.
One thing is for sure, Bottas did an amazing start, but that kind of reaction time is just not possible if you do not gamble and anticipate the lights going off.
So, looking at the slow motion it is pretty clear that Bottas moved a milisecond before the lights went out, but the transponder that records the movement also has a certain time delay (50ms), so if you take that into account, Valtteri did an amazing feat of luck/gambling/feeling by going off at almost exact moment lights went out.
All in all judges deemed he was within tolerances, and that makes it probably the best start ever done by any driver in Formula 1. Check out the video below.