So, if it's behind a flag then people know not to use it, and therefor no one actually uses it. So you can change it if you want, but you never will because you'll never get feedback.

Or, if it's not behind a flag, then you can tell people not to use it, but they will anyway, which is exactly what you want, because then you get feedback. And when you change it, nothing really bad happens.

Sounds like the flag method is a failure, and just releasing it actually works.