So there could be two groups, those who look to improve their skill, who quickly distance themselves from the group that doesn't. Of course, there will still be wide variance in skill between the members of each group. I'm sure you can think of other ways it could happen.
No, I can't. I started out and I sucked. I got better eventually through experience. In order for it to be truly bimodal, people have to start in either camp A or camp B and end in the same camp they started in. Because if you transition from one to another over time, any point in time will capture a group of people in between the modes. Now, you can argue that people don't spend much time in between those modes but you haven't presented any evidence for that. What's more likely is you have geocities coders on one tail and John Carmack/Linus Torvolds on the other tail. And in between are people like the presenter and I. And since I'm not instantaneously going from bad to good, the reality of the situation is most likely some degree of a normal curve filled with people trying to get better at programming or even just getting better though spending lots of time doing it and learning a little along the way.
For all your attacks on the presenter, your argument of a bi-modal distribution sounds more flawed to me. I would love to see your study and hear your argument.