When I was still using Instagram reels, I was always amazed how quickly the algorithm figured me out. If I hesitated for even a second on a reel, it would amend my next ones immediately. I assume the real trick is comparing it to the average time spent on a reel, everyone spends longer on a wall of text reel, but when I stop on a Linux reel for an extra second, I'm immediately in the 1% for engagement.

I read something years ago about how your phone keyboard tracks your recommended words, it knows if you're more likely to type apple or Apple, or if you type soup more than average, and any app that gets that data and compares it to the baseline has an instant, in depth profile on you.