1) In the real world, people need to make decisions quickly and cheaply. We don't always have the luxury to be able to afford paying for or waiting around for the most detailed and complete survey ever. You clearly have no idea what you are talking about. If you want to sit around with your thumb up your butt, and if you want to keep your Data Sharing option on while you use unauthorized software while we get more data, go nuts.
2) You have a poor conception of the question we are trying to ask. This isn't "what is Nintendo detecting." It is an important question, to be sure, but it is much more difficult to answer, and all of the details you mention are important there. But there's a simpler question that these data do help indicate: "how is Nintendo detecting what we're doing?" It isn't the ultimate cause, but it is a mechanism, and that is much more important to us.
3) The people who haven't been banned aren't out of the woods. They might be banned down the road. Or they might not. We don't know. But it can't be said that they haven't escaped detection, so they can't be considered a useful control or comparison.
This is a crude metric, but when precise metrics are just not available, then you do what you can with what you have. And even with our relatively small sample size, it is large enough to establish the credibility of the data sharing being *one* of the possible ways by which Nintendo is detecting our activity and banning us.