Hello M,
Programs can read in the stl no problem.

But the "mesh" data will lose accuracy for something like a mold.

So your model appears to have locating pins!

The difference in cnc with mesh or NURBS data, is the mesh data will have to be cut with a 3d toolpath. Something that just rasters over the outer surface in some way. It wont know there is a perfect arc, located at a perfect coordinate.

Also, parts like the inner edges of the mold cavities will be affected.

A way this would be dealt with is to "defeature" the parts that need mold precision. This is more specialized software, like spaceclaim or others.

Maybe better to use the mesh as a ref and just remodel the part in moi!!!!

2 cents