I completely agree that it is a healthy attitude to have, and all of Apple's claims should be independently investigated. But I also agree that you should check facts or provide citations before spreading FUD:

- There was never any API for a third party app on iOS to get the time spent in another app. The only workaround I saw to this was an app that asked you to screenshot your app usage screen, and it was able to process those screenshots in an automated way (can't find the link).

- There is an API to open URLs between apps, so that one app can link to another app. When developers realized that they could check whether or not a given URL was openable to check if an app is installed, they started abusing this API to check every app on the system. Apple cracked down on the API in iOS 9 and made it so that all apps declare which other apps they can check, and App Review decides if they have a legitimate use: https://developer.apple.com/documentation/uikit/uiapplicatio...