Read the article.
If you were referring to this paragraph...
Scientists believe they understand why the inner core might rotate at a different rate. The flow of rising and falling iron in the liquid outer core generates electric and magnetic fields, which push on the metallic inner core. "The thing is acting like a huge rotor in an electric motor," Dr. Richards said. "Except this one is running a billion amps."
...note that is has nothing to do with gravity, only magnetic fields.
Gravity is a function of mass. Exclusively. It is not "generated" by rotation, magnetic fields or the Great Pumpkin.