I do not know why some of us have a higher tolerance for more alcohol while still remaining relatively functional, but yes, "The doctor's theory that we have an allergy to alcohol [making controlled drinking impossible after we begin drinking]...makes good sense...explains many things for which we cannot otherwise account." ("A.A.", 1939)

Interestingly, however, A.A. *never* declares any part of alcoholism as any kind of actual disease -- no opinion on outside issues -- and no such designation is ever needed by anyone other than for psychological, philosophical or financial reasons.