Almost all nations have chosen this route - which keeps data on your phone and only on your phone.
This is called 'Decentralised'.
But numerous tech guys have devoured the code (it's been made Open Source) and approved it for privacy - which is the point.
The UK Government code is Closed Source - no-one can see what it contains.
The discussion over the API is late on (it's a two hour show!) so FF to 1:48:30 for the start of the piece.
Well worth a watch.
... 'a pretty horrific data grab'.