It could also be "bug driven development". Your README is a specification, and you never do anything that is NOT in the documentation first.
I took this approach in my project here: github.com/ScalaWilliam/eventsourc...
Also you can add some automation to this:
For example, if you added a change in README, you can say in the description "New Issue: thing X is not implemented, does not match readme", and a git bot that I made will automatically create an issue based on that. Here's a commit and an issue:
The fizz buzz example is that of imperative code, it's really better to read the code in that case. Where I'm thinking some sort of visual would be useful is in generating a code architecture view automatically. Like a dependency tree within your code.