When one is hung over (excitotoxicity) you experience a set of symptoms, anxiety, insomnia, GI disturbances, tachycardia, headaches etc. My hypothesis is, since tobacco in itself stimulates neuronal firing exactly like excitotoxicity, and in some studies has actually been implicated in neurotoxicity, apoptosis, and oxidative stress, it may possibly serve to amplify the symptoms of a 'hang-over' causing the user the shy away from cigarette smoking. In the original post two days was mentioned, a reasonable time for the brain to revert to homeostasis, where excitotoxicity is no longer in play, and cigarette smoking can be resumed normally.
In opioid withdrawal I would assume the reasons behind the boost in cravings are different. A short boost in dopamine in addition to the MAOI mechanism could theoretically provide a temporary relief, something which in itself would be inviting for those in opioid withdrawal to smoke excessively. Smoking is also unpleasant physically to people in opioid withdrawal, the dry throat and nausea probably being the biggest reasons. When one compares not smoking because of neurological symptoms, and not smoking because of acute symptoms, I think it could be very different. Smokers are actually not discouraged to use tobacco in some opioid detoxification centers. In withdrawal from gabagenics the boost in dopamine, nor-epinephrine etc and MAOI action could be counter-productive, and serve to worsen the symptoms of a 'hang-over'.
I don't really intend to say the cravings go away because I don't think they do, only that the behavior of smoking stops becoming reinforcing in the case of an alcohol hangover. If there is no mental reinforcement, then the probable scenario is the smoker will smoke to service his physical dependence, which believe it or not, requires only very little nicotine compared to what's usually smoked, and nothing more, in opioid withdrawal it very much remains reinforcing because the symptoms that may discourage the user from smoking are acute and have less of a neurological bearing.
I'm a chain smoker myself also, I find that I tend to smoke a lot during opioid withdrawal, but very little during benzodiazepine withdrawal. In the case of smoking excessively on pregabalin and gabapentin, that's only normal because these drugs dock nor-epinephrine, so the smoker would attempt to compensate for that by doing so. There maybe separate and unrelated reasoning's as well, but based on my knowledge I find this to be the most plausible.