Doubling lifespan is definitely a bigger impact than 4%, but let's explore what the hypothetical "perfect application" of this study to a human life.

A fairly average lifespan is 80 years, so a 4% increase would be about 3.2 years. If I were offered a "wonder drug" that would give me 1,168 more days with a loved one, I would take it.

Obviously that is not how science like this works, but stacking small victories over time is a way to achieve "significant" impact.