Funny enough, for me it doesnt seem to have a lot of data:

- call logs of my iPhone, who and how long/how often i called each person in the last 90 days

- group chat names that seem to have come from the Signal Mac OS app (how is that even possible?)

Looking at my graph the information seems to come from: 1. The native Mails App 2. Notifications

When WhatsApp/Signal send you a notification they seem "leak" the message to the OS. Actually the suspected source 1 (Mail App) could also just be a case of the OS scraping the notifications API.