Is it? News to me. Dr Paul Newhouse gave his non smoking Alzheimer patients nicotine injections and patches, and none had withdrawal symptoms.
Actually I have long wondered if it's addicitive properties are over stated. To me it feels like the breathing and ritualistic aspects of smoking are as much a part of the addiction as nicotine itself. (Probably why vaping is such a good way of quitting, compared to patches and gums).
A case in point - when I started vaping, I vaped with 0mg nic. I didn't notice any significant withdrawl from cigarettes/nicotine. I only moved onto nic liquid because after 6 months of that, I tried one of my mate's vapes and... oh the throat hit was amazing... this is what my vape has been missing... and I stuck with it. But that doesn't take away from the fact that I went from smoking 30 a day for 20 years to 0 nic for 6 months, without the withdrawl.
However:
My tolerance of minor stimulants is pretty high I think. I am the kind of person who can have a coffee before bed and still nod straight off to sleep. But I am in the minority - most people are a lot more sensitive. I have friends who can't drink coffee after lunchtime because they won't be able to sleep that night.
Also, depsite the existance of studies like the one you mention, there are literally thousands of others, equally well regarded, that show how addictive it can be.
So in summary, I think it's fair to say that - yes, it is. But it's complicated.