Many people can edit at the same time in Docs, which is one difference vs a wiki.

"Many people can edit at the same time in Docs ..."

... and see each others' edits in real time. It's very cool.

Ok, but that has nothing to do with Google+ does it, or is it somehow a Google+ feature?

Neither does using a wiki have anything to do with G+. Your original question was about the editing method, not G+ (I think), the person responding to your original question responded to that, and I expanded on that answer.

I suppose the posted article was also really about Google Docs, and only related to G+ because they were using Docs to create information about G+.

The book is about Google+. That's why it's called Google+.