> ensuring that all users of a modern iPhone or Android smartphone will be tracked as soon as they accept the OS update. (Again, to be clear: this happens already even if you decide not to install a contact tracing app!) It is unclear yet how consent is handled, whether there will be OS settings allowing one to switch on or off contact tracing, what the default will be.
I don't think that's correct: you can always disable Bluetooth. Moreover broadcasting, if I understand the documentation correctly, Google and Apple will be providing just general framework: no ID broadcasting will happen until a tracking app is installed. But even if it did, if the tracking keys are not published, it doesn't affect privacy more that Bluetooth MAC address.
> In other words, a malicious app could act as if the user is infected (in a way that is unnoticeable to the user) and extract the daily tracing keys and upload them to the server surreptitiously.
That's true for decentralized tracking not using Google's framework as well.
> This means the technology is available all the time, for all kinds of applications.
In Android ecosystem Bluetooth is available for all kinds of applications too. There is a permissions subsystem that can be applied in both cases.
Everything that Google / Apple Contact Tracing allows is already possible in Android. What it provides is a common standard, implementation, and iOS background Bluetooth capabilities.