Does it show you precisely what you want to see? Or just what you're most likely to engage with? I feel like there's an important distinction there.

The former, which is why people use it. It shows you what you want to see and will genuinely enjoy seeing.

That is why TikTok is more popular than platforms that only focus on engagement, because those platforms will show content that you will engage with even if it's in frustration.

So if I want to see you naked, TikTok will show me it?

It's disappointing to see folks in hacker news regurgitate TikTok marketing material as fact credulously. No service could show you precisely what you want to see. TikTok does it's best - but e.g. if I want to see no staged video, TikTok can't enforce this, because TikTok doesn't know.