This feels like a historical model that just hasn't been updated yet. By directiona linking is missing, yesd it's an obvious one, given or current landscape. It's also understandable why it's not in the list when you understand that the author is using ever note,. And so i'm going to read between the lines here and say that tiago would wholeheartedly indorse that as another retrieval method but he is not going to speak to it because he has no experience with it.