It's not how it works unless you program it that way. You may need to go deeper into the code to do it without warping the coordinate system, but it's possible. And if the planet is big enough, you wouldn't notice any warping effects anyway.
I was also thinking, if you created several different crusts with the number of blocks on the outer radius updated, you could make the planet surface deeper.
I was also thinking, if you created several different crusts with the number of blocks on the outer radius updated, you could make the planet surface deeper.