Indeed, it is not the nicotine that causes the symptoms, but as I have been saying, 'the use of nicotine-alone'. I think I see the confusion now; to be absolutely clear - it is the absence of the other alkaloids that can lead, in some people, to these symptoms, not the nicotine itself.
However, further, it is logical that continued use of just-nic could, for these people, make these symptoms worse, because it will be pushing the imbalance (stoking the craving for the missing alkaloids).
"Some people do just fine on just-nic, and some wind down to zero nic."
A fact for sure. I've always said that those who only nic have a relatively easy path to total cessation. For these people smoking was always more of a simple stimulant for which the other alkaloids did little (beyond aiding the nicotine spike).