The quote doesn't even make sense.
1) If 10 million out of 120 million smokers in India die each year, India will run out of smokers fairly quickly. (India's fertility rate is way down compared to 2 generations ago.)
2) There are at least 400 million adult males in India. Even if that 70% is down to 50% (20% died or quit?), which I suppose 18 years later is quite possible, that's still 200 million male smokers.
In any event, your "first suspicion" is likely correct. 12% of the population "protected" in some way would not affect overall fatality numbers greatly.
I was quoting Raebie’s post.