There is no amount of mental gymnastics you can do to turn “app that tracks when yours and other phones are together and does <something> about it” into something that is inside my moral boundaries.
Then I'd suggest you're not being reasonable at all, because the way it works is entirely consistent with a privacy-first methodology.
That <something> by the way is to take the database that's only on your phone (and never uploaded) and show only you an alert. That's it.
If this is immoral, but letting covid spread around the world and have people needlessly suffer because you refuse reasonable interventions, then I don't know what is moral.
