That doesn’t make sense to me as a reply to the comment above. Such startups should then be useful only for the founder. The GP’s point is to build and get feedback from the users to revise it continuously. That’s how you know you’re solving the problem for someone who seems to have the problem.

The idea is that the founder was once, or still is, the "user". They know the problem because they had the problem, recognized that software could solve the problem, and started a company to make that software a reality.

Because the founder is a user, the founder knows what the solution should look like, and can guide development in the right direction. There's a tighter feedback loop when the user is inside your organization, and is managing the product itself