Really hard to tell if the giveaway is legit or not. I'm not sure either. That's why I haven't given merit yet. In november last year there was a $25 giveaway from a new user and the win was paid out, see here. So all we can really do is wait and see what will happen. 
As with most things, time will tell. Unless there is compelling evidence there is not much that can be said but the OP has made a case that presents suspicions and I thank him for his efforts.