As I said, it's a bit arbitrary. Many projects overlap AVS in their aims or their mechanism. Some, like Placeless Documents and Known Space, overlap in both. Their motivation is very similar and their approach is also similar. They are quite focussed on documents and they are also using attributes in a way that I consider to be a bit limited.
Attributes can serve for much more than holding properties of documents.
But they do take this direction, using them to organize documents into piles. They also mention my point of departure from that kind of system which is to have essentially empty documents and just make use of the attributes. This amounts to a clear confession that everything is not a document. Kala Kala appears extremely good and robust. Kala is highly efficient and secure.