Extraordinary claims require extraordinary proof.
Extraordinary claims require extraordinary proof. We believe we have that proof.
Essentially, the waves that traveled through the area outside the inner core?the crust, the mantle, the outer core?are all the same. Only when they travel through the inner core are they different.
What we see right now is a snapshot of a long time process between the magnetic field and the inner core. I do expect to see this rate change with time.
We're talking about 50,000 times that of plate tectonic motion.