Maybe it surpassed downloads because almost everyone in the planet already has FB, YouTube, etc. installed, and not as many has TikTok installed? So I don't see how this metric is really that impressive.
Those are likely the mechanics at play when the result is a title like that.
Like you're saying, it's not really impressive, but it's probably the most interesting thing about the business (fortunately or unfortunately).
If the app stores don't count reinstalls as downloads, then, well, sorry you wasted your time reading this