The earliest bits of the paper cover the case for significantly smaller life expectancy improvements. Given the portion of people in the third world who live incredibly short lives for primarily economic (and not biological) reasons it seems plausible that a similar calculus would hold even without massive life extension improvements.

I'm bullish on the ai aging case though, regenerative medicine has a massive manpower issue, so even sub-ASI robotic labwork should be able to appreciably move the needle.