Fascinating article, but he left a lot out with respect to magnetic poles. They *do* wander, albeit not as much as scientists used to think (before continental drift became accepted). The motion of the North Magnetic Pole has been tracked across Canada in the past century, and it has moved more than could be accounted for strictly by the motion of the North American plate, especially since it moves in relation to the geographic pole. The reason for this has nothing to do with the crust at all; it's the core that's responsible here. The Earth's magnetic field is not really comparable to a bar magnet; it is not a fixed magnetic field but rather one driven by a dynamo. Conductive material flows around inside the Earth's core, generating a magnetic field, especially as it rotates within and interacts with the solar magnetic field. This is an active process, and subject to a certain amount of chaos. This is why the poles wander, why they can flip, and why they can disappear altogether. In fact, scientists predict that during the next flip, spurious poles will appear at seemingly random points on the Earth, with no relation to the rotational axis. This is broadly similar to what is observed during a magnetic field reversal on the Sun -- the magnetic field is, for a time, seriously screwed up. (That's what drives solar maximum.)
The article also points out that magnetic and rotational axes tend to be closely aligned. This is true, and the cases where it is not suggest strongly that some terrible catastrophe occurred in the planet's history. One of the most famous is Uranus, which has a very severe axial tilt for such a large planet (it's basically flopped over on its side). The magnetic axis is inclined 59 degrees relative to the rotational axis. Even weirder, Uranus' magnetic axis doesn't run through the planet's center -- it's off by about a third of the planet's radius, which is really a hell of a long ways. The planet's magnetic field is thus highly irregular. It is an extremely strange planet, and many planetary scientists have speculated about some massive impact in its history.