This expanding thing should be easy enough to test, surely? And it should be possible for us to do our own tests somehow - actually measure the expansion. So how?
And the seafloor age maps. The oldest seafloor should be just before the supposed subduction zones, surely? Because that material has existed for the longest time. If there's subduction at a steady rate then the seafloor areas of the smallest size should have the youngest age - because they subduct quicker, exist for shorter lengths of time.
I haven't seen the maps yet. Are there such maps in the free pdf's? Should settle the matter.
In the center of the earth is a large amount of trans-uranium elements. As the elements undergo fission there total volume increases.
As an element undergoes fission it starts as a large mass with a small volume. The element then splits losing a tiny amount of mass and becoming two or more smaller masses with a greater total volume.
This has been happening continuously from the time the earth started forming.
Bedrock laid down when the earth had a smaller diameter crystalized into that curvature. A core test would show the stress fractures as the rock was slowly reshaped to fit the expanded earth.
For your consideration.