What you say is true. However, it is only a presumptive diagnosis, based on symptoms and the results of the tests you mention. The biopsy is the gold standard.
Even though I am generally strongly against tests which give you no additional useful information nor additional treatment options, I did have this test. For some reason. I was comforted by the fact that the test directly confirmed that I had a "physical disorder" (less peripheral nerves). Unfortunately, it is also less treatable, even to the extent that most treatments for peripheral neuropathy are usually FDA approved for diabetic neuropathy. New drugs and treatments generally are first FDA approved for diabetic forms. That means insurance generally won't pay for them, although they can be prescribed off label if you're willing to pay for them.