[mynameisbilly]

The people who own the tools decide how the productivity gains are distributed. The workers could produce the same output in less same and go home earlier. Or the capitalists could keep the worker there the same (or more) hours per day and capture the extra output as profit.

Under capitalism, the choice is always the latter. You correctly identified the pattern that Marx described over 100 years ago. The capitalists own the tools and control the conditions of our labor as software developers. They extract that productivity gain as surplus value, and will never choose to willingly give us more leisure time.