I've seen research indicating that tobacco users actually cost the Canadian healthcare system less overall: they die ~5 years younger, and healthcare costs go up with age.
Obviously I know this isn't what you're arguing. You're right in saying that alcohol and tobacco taxes aren't used to offset higher costs to healthcare. In most cases they're supposed to be a cost pressure to change consumption.
E.g. healthcare costs go up with age because that's when people start dying. Smokers die at an earlier age, so they experience those costs earlier. Is this correct? Who knows, but it's one of the many ways in which the argument you wrote could be invalid.
Furthermore, healthcare costs don't reflect the complete picture. Firstly, lost productivity is an issue. Secondly, we may not want a society where ritual suicide is encouraged at a pre-determined age with the goal of reducing healthcare costs.
Smokers are subsidizing everyone!! How do you solve for that?