Software is clearly an exception to this because you can leverage your work to an arbitrary degree. One person can write software that benefits hundreds/thousands/millions/billions of people.
The junior engineer solves an immediate problem. The senior engineer realizes it’s generalisable to similar problems of their team and solves them all at once. The principal engineer realizes it’s generalisable to their entire company (or broader industry) and solves it for everyone.
The relevant metric here is not how much code you can write or quickly you can write it, but how difficult and impactful the code being written is.
Many widely-used and industry-shaping pieces of software were (at least initially) the product of just a single programmer, or at most a small handful of core developers. When other people joined it, it is often after the software had some initial success.
The junior engineer solves an immediate problem. The senior engineer realizes it’s generalisable to similar problems of their team and solves them all at once. The principal engineer realizes it’s generalisable to their entire company (or broader industry) and solves it for everyone.