But can't you see how coming out with a strong statement like "i've been doing this, it works" before your app even has a single user and before you've had to contend with any externally filed bug reports and keep the app stable as you fix those and add new features isn't very reasonable?

If anything there are clear counter example to your claim, such as the major provider agent harnesses which are all almost always fully vibe coded, and riddled with bugs and regressions that make using them painful for users. The only reason people put up with it is because competition in the space is still limited.