> A while back, when I was curious about TikTok, I downloaded it and was instantly swiping through a video feed that was already getting customized for me.

Has this been definitely proven though? I tried finding evidence of whether TikTok tailors content for unregistered users (based on their location/device for example), but so far, I could not find a page that would even clearly ask that question. Every article about the algorithm I have read only considers registered users...