Hi Lupin,
Sorry you had a less than happy experience.

With PN you have to rule out a lot before you get to the diagnosis.

Here is my experience just to show you how its not a 1 shot deal..

First I was given an MRI to test for MS and stroke. (it was clear)
I was also given blood tests as they wanted to make sure I didn't have Myastenia Gravis. (I don't)

Then they gave me my first EMG.. which showed I have a demyelinating with secondary axonal loss.
So they sent me to Mayo.

At mayo I was given a full body CT scan, and 6 vials of blood were drawn.
I had another EMG.

They found nothing wrong other than my EMG.
I was told to come back if my damage progressed.

I didn't want to drive out of state, so I went to another neuro..
She just did a spinal tap.
And I have another EMG tomorrow.

She may be doing a nerve biopsy.

However, at least I know what they are looking for.. because we know the damage type because of the EMG.

I think your neuro is just going on with testing to see what could potentially be abnormal since you have had normals in the peripheral system, he/she is checking the central nervous system next.
Which makes sense.

I wish you luck with testing.
Its the least fun part of everything, and lots of us wait a while to have some sort of track to follow.