The pole shifts are a story that is being told over and over to the new generations in the real world.
They are used to explain away certain changes in the environment. Such as with the polar vortex.
Or with the disappearance and weakening of what they call the Van Allen Belt.
It's a load of crap in the end. Just like the idea that is entertained by some that volcanos supposedly produce electricity. It is the other way around. Volcanoes themselves are of electric origin in the real world. Yada yada particles from the sun that slow down as they pass through earth and some stuff. I'm not here to hold a university lecture.
But basically, this girl is good at learning. But she learned the wrong stuff. The reason that so many Japanese works feature and regurgitate these same ideas over and over, just like what Oda is doing today, is because they are getting paid to foster a narrative. You could see it as a form of 'sex sells', a kind of handbook to successful writing. You can't sell certain information people and expect them to buy it. So instead you have to stick to that which people will buy.
Which is not to say that Oda can't be a lameass and follow that script. Quite the opposite. But the actual meaning behind One Piece goes deeper than the magnetic nonsense she talks about.
The pole shift of the Earth is something that is said to occur at odd intervals in the real world every variable X thousands or tens of thousands of years. That does not include the shift of the sun, which is also said to happen around every Y years. The story Oda is telling is not about magnetism or pole shifts, even if that may seem like the major theme that is going on. The actual story of One Piece is about the Earth and the devil. But you won't understand it if you lack the knowledge of the symbols that are being used in the manga constantly.
The moment someone starts talking about electromagnetism to explain One Piece or by extension the real world, they are dumbing everyone down who listens in.