[derbOac]

Would such proof be available?

I'm another one who's tried TikTok on a number of occasions and it's always failed badly with me, worse than any other site I can think of. It never improved despite people telling me it eventually would.

My impression is that it was making too many assumptions about me based on the wrong signals or something.

But to your point: wouldn't there be a survival bias of sorts with assessing recommendation performance? I didn't like it and left, so presumably the people who remained liked it.

It's obviously popular so there's that, but it seems circular to say it's working for the people who like it and stay. You're losing information about opportunity costs of lost users.