Within ManagedSettingsStore, in the documentation for the ShieldSettings.ActivityCategoryPolicy enum (here), one of the options is all(). It states that if this is used, the device will shield "all apps and websites".
In practice, I have noticed that when this is used, a handful of apps (i.e. Messages, Maps) remain unblocked. Furthermore, it appears that on different devices, this usage results in different apps remaining unblocked (on my device Messages remained unblocked, but on another tester's device Messages was blocked).
Can anyone provide clarification as to explicitly which apps are not included in the specification of "all()" and whether this changes based on device, iOS version, etc.?