I think function naming is very important here.
A heavily dissected function can be very self-documenting. If each logical process within a function is split out into its own function, with minimal internal logic, then the behavior of each statement can be reasoned out by the names of the functions and the parameters they take.
Of course, there is a downside: the function names. Like comments, such highly specific functions can often get out of sync with what the function is actually doing. But, at the same time, by giving it a proper function name you make it harder to justify scope creep. It becomes more difficult to make a sub-function do something more than it clearly ought to.
So I would suggest this. If you believe a section of code could be split out, even though nobody else calls it, ask yourself this question: "What name would you give it?"
If answering that question takes you more than 5 seconds, or if the function name you pick is decidedly opaque, there's a good chance that it isn't a separate logical unit within the function. Or at the very least, that you're not sure enough about what that logical unit is really doing to properly split it out.
But there is an additional problem that heavily dissected functions can encounter: bug fixing.
Tracking down logical errors within a 200+line function is hard. But tracking them through 10+ individual functions, while trying to remember the relationships between them? That can be even harder.
However again, semantic self-documentation through names can play a key role. If each function has a logical name, then all you need to do to validate one of the leaf functions (besides unit testing) is to see if it actually does what it says it does. Leaf functions tend to be short and focused. So if every individual leaf function does what says it should, then the only possible problem is that someone passed them the wrong stuff.
So in that case, it can be a boon to bug fixing.
I think it really does come down to the question of whether you can assign a meaningful name to a logical unit. If so, then it can probably be a function.