It depends on the pressure over a certain area. If molecules are more pressurized and have very little expansion then the force of one object will effect the other. I could link articles that state that there is very high pressures in the inner part of the Earth, especially near the core. Such larger pressures make forces acted upon by expansions more influencing on other parts of the Earth.
I interpreted the analogy as when something is expanded by an inner-object's expansion then at some point the outer material will eventually begin splitting at certain points, especially when the material is not stretchable past a certain point and the brittleness of certain materials requires less pressure force upon a specific area of a material to make it cause fractures within the material.
Again, it depends on the many factors that exist, such as pressure as I have brought up many times before.
To put this whole debate to rest, here is a specific requirement for the hypothesis to be true.
As many will know, the Earth's distance from the Sun varies throughout the year. This would affect the strength of the coupling of the Earth's and Sun's magnetic field. This would also cause the energy density to decrease between the coupling of the magnetic fields, therefore causing less energy to be within the coupling of the magnetic fields.
As you had stated before, there is also heat lost over a period amount of time. This would mean that in order for this hypothesis to be accurate the thermal energy increase of the Earth's core would have to be larger than the thermal heat released from the Earth. Involving both factors, one requirement of evidence would be to detect an approximate trend of the above. In order to detect the trend, there would have to be an analysis of plate-tectonic(more specifically, Earthquake activity or other forms of plate activity such as volcanic activity) statistical data. If this trend is detected within this type of data consistently throughout each year, then this is starting evidence of the hypothesis.
EDIT: I forgot to explain the equations.
The first equation is describing the linear expansion of the material that is of focus based on the required expansion, where you take the coefficient of expansion(such as iron) and multiply it by it's original diameter. This is, then, multiplied by the change in temperature. Q2 and Q1 describes the thermal heat of the iron core at different times. The mass of the iron and the specific heat remains in the same range therefore it is not changed.
http://physics.bu.edu/~duffy/py105/Temperature.html
The equation can also be represented as [math]L=\frac{\alpha L_{1}\left (Q_{2}-Q_{1} \right )}{mC}[/math]
EDIT: Of course, what also must be taken into account is solar activity within that year as well. This must be accounted for within the evidence.
More specifics of the evidence, if this trend is detected, is to see accurate values from the equations above. Of course, more would have to be added to the evidence, such as equations for pressure upon the crust of the Earth based on the expansion of the iron core. These are still being developed.