IMO, shifting the thread into a discussion of "addiction", is a disservice to the conversation about the differences between people that allow some to switch immediately, some to take some time, some to do both, some to give up vaping etc. Giving the question a label that implies that all people are the same and if they haven't quit they are in denial shuts down the conversation.
Addiction has become a catch all term to define any behavior that provides pleasure and that we don't want someone else to do. I'm not saying that it's not a real thing, but that the word and concept are misused. Over use of the concept means that we can't search for answers anymore, cause the only answer is addiction. Not very helpful, and minimizes the heck out of what people go through on the path to sobriety.
Addiction in the context of substance abuse means that the substance and behavior interferes with daily functioning. And yep, the 12-steps work for a reasonable proportion of people.
There are physiological responses associated with physiological addiction, specifically release of dopamine from the nucleus accumbins. The problem is that everything that feels good, or anticipation of anything that feels good causes this dopamine release (food, sex, stuff that helps us survive). Addiction hijacks the biological pathway, and some substances really mess up its natural functioning- so that nothing feels as good as the substance.
But, dealing with addictive behaviors, drug seeking, denial, symptom substitution are all in the realm of the psychological and even with the biological underpinnings there are as many ideas about what addiction is as there are people who take the time to think them up.
Carl Phillips says it much better than i do
Does ANYONE have a valid definition of “addiction”? | Anti-THR Lies and related topics
Searching for what works, learning about peoples experiences and any commonalities that exist is important, because maybe we can find the ways to best support the different subgroups of people (those who need nic, those who need WTA, those who need visible vaper, those who want the fiddle factor, those who get overwhelmed by the fiddle factor etc)