That's a fair point, but if we're imagining a world with a twenty hour work week we can also imagine a world where life's basics aren't made unaffordable by capitalist greed.
OH MY FUCKING CTHULHU, THAT IS NOT HOW YOU USE A FUCKING PIE CHART, THE VALUES AREN'T EVEN IN THE SAME TYPE AND WHY IN THE NAME OF EVERY HIGHER BEING THROUGHOUT HUMAN HISTORY DID YOU SCALE VALUES WHICH ARE CONVERTABLE (20h and 4 days) BASED ON THEIR LITERAL VALUE????
With the proliferation of automated production combined with a rapidly increasing population, limiting the maximum work week (where practically possible), that employers could force employee's to take (so not including voluntary overtime), could be one of many possible solutions to rises in unemployment, by artificially increasing the amount of workers a business would need to hire to maintain productivity, while simultaneously allowing those workers a greater amount of time to themselves to do with as they wish.