As I said multiple times - doxxing can use public databases and social media to gather that information. Read the wikipedia definition, it is right there.

Imagine a vtuber posting a photo on their private facebook. Then their neighbors grabbing that photo, knowing they are said vtuber, going to the fandom, linking the photo as "this is the vtuber, they live at XYZ". Would you still go "oh that's not doxxing, they posted their faces on the internet that one time!"? Of course you wouldn't.