The difference between TDD and FIT

Here James Shore makes a great differentiation below:

"...Fit examples are not unit tests. Fit examples are just that: examples of a business rule in action, from a business perspective. In TDD, I write tests for every line of code that can possibly break. In my Fit examples, I try to talk about every possible business case. That's a bigger net than TDD, and without TDD, my code wasn't well tested."

James calls Fit "Storytest-driven development" or "STDD" (despite the stigma) I think it sounds like a super Agile concept. So is this where the "user terms of acceptance" from the nebulous "user story" get converted into arguments in the FitNesse wiki? This is a good picture of executable documentation. (Now this is where imagination is needed) How can all the varied and complex features of a solution be represented in a Fit test?