In a world where various technology curves are going through exponential improvement, this seems like a false mental model. Scaling yourself out as a manager may offer some kind of linear multiplier over raw output, but hard to say without context. (For example, if you are a strong contributor managing weak contributors, the net effect may in fact be negative in terms of raw productive hours.)

However, that linear multiplier doesn't mean jack in a world where technology can create exponential leverage. I'm pretty sure on a given day, the potential for a single or small set of individuals (without any centralized management) to produce products and systems that change the world is higher than any day previous.