In theory, NJ, as I was saying above, the app ought to be able to deal with scenarios like the above,
However it doesn't appear, at the moment, at least, to be all that accurate. I dread getting a notification, which would almost certainly be spurious in my case, telling me I've effectively got to stay in my room for a fortnight, with no prospect of getting a test. While my family, who may have caught the virus off me, can do as they please. And all the while all of us might be, as it seems the majority of cases are, asymptomatic, and yet equally infectious.
The fine for non-compliance has it seems quite arbitrarily been imposed, as have fines, actually, for wilfully condemning someone you don't like to house arrest :-)
I'd be much more comfortable with all of this if testing was available in such situations, but unless you develop symptoms it isn't (and even if you do it seems problematic)
If the new vortolex testing technology comes off then that could dramatically change things. But I've lost count of the number of technological breakthroughs which were going to be "gamechangers" and never happened.