You need to separate the HOW from the WHY. I agree that splitting a column into two is a potentially useful idea. But just because it's not a common pattern doesn't negate responsive design: it just means it hasn't been figured out yet.
Responsive design is an insight that is slightly ahead of it's ability to execute. But don't throw the baby out with the bathwater just because it's not clear. The insights that come from this approach, even if you just make minor tweaks are far reaching.