The best I could interpret it is to have it both ways; break it down into small private functions, then nest (edit: encapsulate) these in a larger one where they can't be seen by anyone else.
It depends on you and your team, the project requirements, the rest of the codebase, and so many other things. The choice you make is less important than _why_ you make it.
> Master Programmer: "You fool! You can't just stuff all your code into one function because it's easier to write!"
So the Novice Programmer separated all the code out into different functions and showed the results to the Master Programmer.
> Master Programmer: "You fool! Why have you broken this out into different functions when it all belongs together in the same function?"
And in that moment the Novice Programmer achieved enlightenment.