The story format makes the point land better than a legal summary would. Most founders who vibe code a product never ask who owns it until someone else has copied it.
The questions near the end are the practical part: a custom design file, manual changes to the generated code, and a written architecture. Those are also the things that make a product maintainable, so the work that may protect authorship is the same work that keeps the app from falling over at 300 users.
On client builds we treat ownership as part of the scope, not an afterthought. The brief says who holds the repository, the cloud accounts and the design files from day one, and the architecture is written down by a person before agents generate anything. It costs little and answers the lawyer's question in advance.
Have you seen founders try to document human contribution after the fact, and does that help at all?