We adopted the "com.apple.developer.family-controls.app-and-website-usage entitlement" to read usage through "DeviceActivityData.activityData(filteredBy:using:)" after "approvedWithDataAccess". It works as documented.
We want to clarify the exclusivity issues. The consent sheet says, under "Limited Access", that Screen Time "will lose access to this data as only one app or service can access it at a time." On our test devices that is exactly what happens: after allowing, the Screen Time pane in Settings shows no new usage until the app is toggled off under Apps with Screen Time Access. Is this intended as permanent design, and is there any supported way for a third-party app and Apple's Screen Time to hold the data simultaneously?