Productivity is a form of activity, not a quantity.
Systems of productivity that are organized by wage remuneration rely on processes of labor valorization, but no such process reflects any inherent or essential feature of the productive activities undertaken by any individual worker.
Production in enterprise is by social processes.
Processes of valorization have more cogency at the level of the entire enterprise, because products within the enterprise are created through the complex accumulation of many individual contributions, but are exchanged between easily separable entities, one enterprise with another, or an enterprise with a consumer, often through commodity markets.
Ultimately, there is no law of nature for resolving a distinctively quantified value of each worker’s labor.
Similarly, there is no law of nature proscribing the same rate of remuneration to each worker per unit of time contributed to the social processes of labor. A social choice for such practices would be possible to implement.