>unlike an app, where too often uninstalling the app simply means an icon is removed from your screen, but some data is still retained as a file somewhere on the device.
What is this referring to? On iOS at least deleting an app means the app and its data is gone for good, except for keychain data. Same with android, except for on sdcard/internal storage. But in either case the developer would have to go out of their way to store data there. If they're being malicious they might as well upload the data to the mothership to begin with.
They are referring to the ways that contact tracing APIs are implemented at the iOS and Android level, and apps just utilize the API. I believe the article is speaking to the APIs (Android and iOS) and how they implement contact tracing independently of third party apps, which use the APIs.
What is this referring to? On iOS at least deleting an app means the app and its data is gone for good, except for keychain data. Same with android, except for on sdcard/internal storage. But in either case the developer would have to go out of their way to store data there. If they're being malicious they might as well upload the data to the mothership to begin with.