It's outdated advice in 2025 IMO.
1) We had this methodology for over a decade now. Most of the business models that work with this have been mined out. The features that increase customer sales by 2-3x are the ones that nobody asked for.
2) Building prototypes is cheap. Like easier than making videos or slides. You don't need $100k and a few months to build features anymore.
3) Landing pages, wishlists, and product hunt have become a smell that these guys have no idea what they're doing. They're validating. The docs are incomplete, there's some tutorial videos on a screen that doesn't exist. 2 weeks later, these companies tell me they're pivoting to something agentic that I don't want.
Fuck that. It took us 3 days to build it internally. The logic for SaaS was that it caters for edge cases and maintenance that we don't want to do, but these modern SaaS don't want to do it either. If they knew what they were doing and if they cared, they wouldn't be playing the wishlist game.
Have some confidence in what you build. Do it better than your customers would do with Bolt or Lovable.