A good UI example is the widget with the hierarchy view.
If it would be possible to sort the view, it would be almost like a directory window.
The same could apply to the flow. Honestly, nobody has a problem with millions of entries in a directory. You sort, search and just scroll up and down. And here we would have filters too.
The key is the view configuration.
Sorting and filtering would be essential.
If you show all backlinks by default and give the user the power to filter them, everybody can make up his own system.E. g. filtering for Folder objects. 
In an object orientated system, you have relative directories. You define a starting point and look at all children. That’s how the widget does it, and it works perfect. (Except for the missing sorting and filtering functions.)
Actually, people like me love directories because they really direct you to the right drection
And if you could set a filter for the flow, you could reduce multiple parents with ease. You could, for example, set up a directory attribute and just look for all elements in the hierarchy that have this attribute active.
The possibilities are endless and users are very creative in finding their ways.
That’s why I would rather give more options and let the user choose.
To make the people know, it’s rather a question of documentation.