It works for some people. It's also completely free, which you can't say about medical intervention. Around here, detox and rehab facilities have 6 month long waiting lists and cost tens of thousands of dollars.
I am skeptical about that too. I'd be surprised if both rehab and AA don't have a statistically significant effect on addiction treatment.
People tend to expect that rehab will cure addiction, and become disillusioned with the reality that addiction is a chronic illness. Relapse rates are high in chronic illnesses, like diabetes and hypertension, the latter having a relapse rate of 50%-75% according to the NIH. Addiction is no different, and its relapse rates are between 40%-60%, even with ongoing treatment. Efficacy rates will reflect this harsh (and often very expensive or deadly) truth.
Also instead of taking the time to write out multiple comments expressing your doubt as to the efficacy of AA, you could've found the information you needed in a single google search.
I am pretty skeptical of a claim like that.