I'm fascinated by this idea of a deep web only accessible by the cognoscenti. Presumably if a link slips out then the deep web becomes a lot shallower?
It is non-obviously difficult.
It just has that feel of "secret society" to it, which tended just to reflect the informal power structures of the wider world anyway.
So it is a "collection" of secret societies, each with their own quirks. As a collection is constitutes a 'web' and perhaps the only commonality is the desire to not be part of the "public" web.