The physical dog doesn’t think—its non-physical brain does the thinking. It makes sense, then, what it is about the out of control dog that makes it out of control—its brain isn’t present. There’s also a switch between the two from physical to non-physical and back. We have no idea what that means, or how hard it is.
In the mountaintop metaphor, the size of the brain boulder matters, too. Some breeds have characteristics that has the physical dog‘s boulder many times larger than its brain boulder. There are even personality differences that will contribute to different relative sizes of the two. Generally speaking, it’s not about shrinking any sizes—it’s about having the interactions, the consistent interactions, and the repetition of the interactions to bring the smaller of the two up to the size of the larger one.
The puppy is born with its physical dog in charge. The adult dog learns to have its brain online more than its physical dog. Those are the adult dogs we like. It looks like obedience, but it has more to do with the battle between “the brain” versus “the physical dog.”