[member="Liliane Lancaster"]
To be technically fair, although you have a point, most of those groups you mentioned began as faction (in canon) specific groups. The Jedi canonically belong to the Galactic Republic (or its later incarnations), the Sith to the Sith/Galactic Empire, the Witches (of Dathomir). They didn't become generic until they were here in Chaos, and multiple factions began hosting their own version of the Jedi or Witches or whatever.
If you were to continue down that line of thinking, we could simply say that any tags besides Jedi, Dark Jedi and neutral are superfluous and need not exist. Witches, Sith, Rogues, etc can properly fit into any of the three tags based on alignment, which is a better way to distinguish than their specific qualities, right? I mean, Sith and Dark Jedi are just dark force users, right? Witches could be dark, or light or neutral, depending on how the character is played. And rogues could use the light jedi or neutral tags, depending on their alignment, too.
Except we do have tags for specific groups. And that's okay. I think the question has been mostly settled, the Knights of Ren need to grow a bigger population and demonstrate their unique angle here on Chaos. That should settle the question of whether they are an established part of Chaos lore. But they won't stop being a niche group, undeserving of rank tags, until one important group says so, our staff. Until that day, rationalizing and minimizing their importance is irrelevant in the greater scheme, and it'd be better to focus your energies elsewhere.