> Q: Wouldn't this list be insanely long? More so if it doesn't have any concept of location?

I don't think such a list would be that long:

1. It's not unreasonable to have some approximate concept of location (e.g. "New York City and surroundings")

2. A contract tracing app is only useful when the number of new infections is low enough, such that all possible contacts can be tested.

3. For a tracing key 32 bytes would suffice. Even for 15,000 relevant infections you're only looking at 0.5 MB of data.