Anything you do to escape a block becomes a secondary behavior. Every speaker has occasional repetitions, usually initial, but they are hardly noticed because they are not a big deal. The repetition to escape a block is a different kind of repetition. You can see a great example of a non-stutterer's repetition on the video just posted here of Alex Turner inteview at 5:30. That is a standard repetition. In the example you gave of going back to 'r' , lets call that an "escape repetition". Can you see how it's different from what happens at 5:30? ​ Edit - people who are fluent have hardly any emotional thought toward their repetitions. If we get stuck in the middle of a word, give up, and have to backtrack, there's bound to be an emotional component - making it a different entity. Ultimately, I think the difference is whether there is an emotional component.