I think the GP just means that the tail of the age bell curve seems (surprisingly) short to them.
The implication being that when doing statistics with a large number of data points, you often see several outliers that are way outside the curve. In the case of age, the tail of the curve falls to 0 very quickly.
We've done a lot to shift this away from a normalized curve, which feels very unfair to us as humans, to one where more people have a chance to live to a longer age. We've spent much less effort trying to extend the longest lifespans. This seems totally rational to me.
It seems strange for some people because they imagine this "average" as a classical mean and the intuitive shape of the bell curve - the biggest chunk must be in the middle ("for every child that dies at birth someone must live to be 160 to have the 80 years average where most people should be") rather than a statistical life expectancy. We substantially reduced a lot of the external factors killing us early (disease, war, accidents, etc.) and we're hitting the real limit of human lifespan. We haven't addressed this because we don't have the tools yet. So all the work was to push the curve to the right because that benefits most people and it has a lower threshold to achieve this, without actually pushing the tail end further right because it benefits very few and it seems like an impossible task today.
The average speed for an F1 race might be 250Km/h. This doesn't mean any of the cars can ever hit close to 500Km/h. Just that we eliminated most of the reasons cars were slowing down and were left with the fundamental limits of the car's speed as dictated by it's engine, grip, aerodynamics, or weight.
The implication being that when doing statistics with a large number of data points, you often see several outliers that are way outside the curve. In the case of age, the tail of the curve falls to 0 very quickly.