> Has the last 70 years of productivity increases led to a reduction in weekly work hours?

Yes, it has led to a significant reduction in hours worked: https://ourworldindata.org/working-more-than-ever

Of course, the effects aren't equally distributed across all countries. For example, annual work hours per worker have almost halved in Germany since 1950, but only seen a more modest decrease in the US. So political factors still play a role in how the benefits of increased productivity are used by society.

But it's a strong effect. And those numbers don't even consider other factors such as how increased life expectancy combined with mostly unchanged retirement age, and being older when we first start working, give people an extra decade or two of not being part of the workforce at all.