alt Hacker NewsThe simplest explanation would be that Instagram crawled my TikTok's account's followers and is curating my Instagram reels based on that point in time.
However that's not what happened, because my "following list" is restricted to be viewable by "only me", even though my account was public. "Public" just means that you can view my videos without me accepting a follower request. And I don't have any videos anyway.
So I can only deduce that setting it to "public" flipped some bit in either Instagram or TikTok's backend to where now they both are sharing the same or very similar data to curate my feeds.
In the book "careless people" it is highlighted that Facebook embedded spyware in their app which tracked other apps that were installed/used on the phone. This allowed them to figure out that so many of their users were installing WhatsApp, and enabled the legendary WhatsApp purchase. It is very much possible that Instagram is reading some sort of temporary files created by TikTok and extracts data using this method.
Facebook/Meta has a proven track record of fetching all data from your phone, even when abusing security vulnerabilities to do so. And the clowns at Apple can't even fix RCEs in their network-exposed applications, I'm not convinced the separation between apps is flawless.