It’s not tautological, it’s the difference between giving someone twice as many heart beats, vs making their heart beat half as fast.

Even if we figure out how to do the latter, it doesn’t help folks who have already had most of their heart beats. It’s not actually life extension.

And what is life like lived at half speed? Let’s say we can get people to 200 by keeping them immobile and cold and nearly starving them of calories and oxygen—dramatically suppressing their metabolism. Who would want that?