Not allowing excavation to the core solves weird gravity issue as well. Astroneer had super weird gravity at their planet core. You can get stuck oscillating there.
That actually sounds pretty close to what I would expect to happen IRL. After all the mass is mostly all around you at that point and depending on how far you are towards the core you might build up speed, overshoot the target and then do it all over again.
But hollow planets are hard to come by so this is just my imagination, I'm sure someone has worked out exactly what would happen.
I think the outer wilds did this perfectly. I seem to remember falling towards the core and gravity just disappearing.
If you really wanted to go for realism, there would be NO GRAVITY at the core. :P
As you dig down you would get lighter and lighter on your feet.
Any mass you are below (within the sphere of Earth) will exert a gravitational pull in one direction, while the mass above you (also within the Earth) will exert an equal and opposite pull.