I'm not sure if this is very obvious or very interesting. Let me know what you think.

" I can't imagine anything else you can possibly store about relative elements besides index and order (and nothing). Graphs are their own other planet, and I don't think we can easily say much about them. So the 3 data structure types you can have are:

1. indexed data structures with an O(n) worst-case operation

2. order-less data structures with an O(1) worst-case operation

3. sorted data structures with an O(log n) worst-case operation

That's it. Let me know what you think"

I disagree.

sorting is a O(n*log(n)) worst-case operation for example.

The article explicitly states that sorting is O(n log n), giving rise to log n per element. I think you missed that I'm talking about adding/removing/reading a single element at a time.