There is a lot of scientific evidence accepted by the broader medical community that the mental attitude of the patient and their active participation in a treatment plan is critical to a successful outcome.
Consider that the 12 steps is a treatment plan. The fact that it has a spiritual foundation is coincidental..evidence has also pointed out that spiritual faith changes neural pathways in the brain.
The allergy argument is relevant in that some people cannot physically tolerate any alcohol with displaying deleterious effects. I doubt I will get hives or go into bronchospasm if I drink a wine right now but I'm certain the effects will be deleterious and result in a descent toward active alcoholism given time.
Addiction is a complex mental, physiological and spiritual disease that is best treated using a range of modalities that address these multidimensional aspects. The 12 steps go a long way in addressing the mental and spiritual aspects of the disease for many people. Always keep an open mind. Doctors of western medicine are thankfully becoming more open minded about disease, it's causes and treatment. So should people in general.