What % would you expect to be affected by the placebo?

I think most adults are in a steady state for their habitual behaviors around diet / exercise / drinking / drugs. Would be surprised by anything larger than 10% change in control tbh

FTA: "helped people with alcohol use disorder reduce drinking for at least eight months after their first treatments, results from the largest clinical trial of its kind show."

This isn't a genpop study.

Also, both prongs were given psychotherapy, also.

Is it that hard to imagine twelve psychotherapy sessions convincing someone to quit drinking for eight months?

Have you ever met an alcoholic?

Yes. I've also met former alcoholics, and people who quit for a while then started drinking again. Twelve weeks of therapy leading to eight months of sobriety for 25% of people does not seem surprising.