Sure, but the problem is that there is not enough of a young population to support the older population. So if the life expectancy drops because younger people are dying more, that just makes the inbalance even worse, with the population being even more top heavy.
As a thought experiment, if you killed everyone when they turned 70,that wouldn't worsen the imbalance, it would help it. It is more of a question of the type of death, and the onset of disease.
There are broad classes of life extending Healthcare that you could remove with minimal impact on worker productivity, but still reduce life expectancy. Simpler yet, you could just deny oncology or cardiovascular treatment for anyone over 65. Life expectancy would plummet with no impact on workers.
I'm not saying I agree with this approach, but rather saying that someone who points this out is not misunderstanding the topic.
Furthermore, like it or not, this type of cost benefit analysis is baked into the treatment analysis of every country on the planet with socialized medicine.
