Why would they do it in secret? It's a "feature" they really want to use as a PR opportunity. They just messed up the first announcement.

One thing that was slightly confusing in the initial announcement was that it was said to be released on a day when no OS update was happening[0]. I've been unable to find details of how the rollout was supposed to happen, but if no OS update was needed the code would have had to already be deployed in a previous update before it was officially disclosed by Apple, wouldn't it? I don't know of any sources that show it was present and if so whether it has been verified that it was removed, but if such sources exist I would appreciate references.

EDIT: This announcement from Apple says it was to be included in an iOS 15 update when ready [1] so unlikely it was just dormant in some previous update.

[0]: https://news.ycombinator.com/item?id=28068741 [1]: https://www.apple.com/child-safety/