What you've said largely tracks with my interpretation of Apple's actions here.
> I feel that to provide a full experience for the review team when you ship a feature flag you really ought to list all the behaviors that the app can possibly have, and let the review team test that if they want.
After Epic added direct purchase gated behind a feature flag to Fortnite, I'm genuinely surprised Apple didn't start requiring full control over and documentation of all downloadable configuration files as part of App Review.
While being vaguely on the side of review being not very useful I would agree with Apple doing that if only to make their position more consistent, even though I am sure every developer would riot if this was the case. (Although I vaguely remember someone saying we provided feature flags to Apple when we submitted builds at Twitter. But do take it with a grain of salt, since I wasn't on the release team and my view of them is vaguely positive in that I think they generally didn't try to use tricks to get through review.)
Odds are their "front line" reviewers are not highly technical, so Apple wouldn't want to commit to that. They are more than large enough to afford a few inefficiencies and pick fights the few times something like iSH "slip in".
> I feel that to provide a full experience for the review team when you ship a feature flag you really ought to list all the behaviors that the app can possibly have, and let the review team test that if they want.
After Epic added direct purchase gated behind a feature flag to Fortnite, I'm genuinely surprised Apple didn't start requiring full control over and documentation of all downloadable configuration files as part of App Review.