Ofcourse you don't want users to lose the feature once they exceeded your revenue threshold or cross the border so you'll need to implement some kind of tracking. Your analytics and error tracking also needs to communicate with the feature flag service.
Definitely not rocket science but more complex than a environment variable.
That is, features are contractual and when you've only got 50 customers but they're all paying high 6 figures does anyone really care about feature flag complexity?
"The customer would like the main page blue and another one the red". Would it be feature flag for you?
Not just an argument, it's the entire point of feature flags for ui experiments which is an essential practice. Dynamic adjustment of the cohorts (or even just an immediate kill switch if it's a disaster) is required.