> seeing as it’s fully local and doesn’t leave the device

Running the tool on my Macbook (which I don't really use, but which is logged into my iCloud) shows tons of activity/names/contacts that's shared ("donated" in the system's terms) over from my iPhone, which I wouldn't have expected to synchronize to this laptop. The apps aren't installed on the laptop, I don't get notifications there or have any interaction with those people. I can even see some stats showing volume of activity on work apps installed on my phone inside a managed work profile, but it does seem to have filtered the actual contacts out.