Not trying to defend App Store policies, but writing this just for those who are struggling with Guideline 4.2 trying to publish an app that is only intended for a small group of users. There is a less well-known option called "unlisted app distribution", similar to unlisted YouTube videos: the app is public and can be downloaded using the direct link, but it cannot be found in App Store search. The "small, or niche, set of users" guideline normally does not apply for such apps.

To request unlisted distribution for your app, send it for review as usual, then file a special form [1], and mention that in the review notes.

Source: I struggled with Guideline 4.2 when I tried to publish an app showing the bell schedule and other local information for the neighborhood school. Its audience is, indeed, not of Apple scale: the school parents living nearby. Apple refused it as 4.2 and only agreed to publish it as unlisted, which I was okay with, because sharing the link between the parents was not a big deal. Google had no problems with publishing the Android app normally though.

[1]: https://developer.apple.com/support/unlisted-app-distributio...