Guy, I've added an Issues Status section P3126 Overview to capture the discussions in this reflector an elsewhere. In the section discussing BFS & DFS and the possibility of using coroutines, I've added the following text.

The purpose of the standard library is to adopt standard practice. If we propose the use of coroutines, it is different from the use of visitors by boost::graph (written around 2000) which is the closest to a de facto standard available. It will be helpful to justify using something different ahead of time to smooth the process.

Does this reflect what you have been saying? (Feel free to edit and give me better text)