Explain why retained goal-directedness, despite the inefficiency, is what actually defines circumstantiality rather than simply talking at length.

Many people give long, detailed answers without this representing any disturbance of thought at all — verbosity alone is not circumstantiality. What makes circumstantiality a specific clinical finding is the combination of excessive, unnecessary detail with the underlying goal of the conversation being retained throughout: the person has not lost track of what they were asked, they are simply unable to get there efficiently, weighed down by tangential detail at every step. This is precisely what separates it from more disorganised forms of thought disturbance in which the goal itself is lost, which is why the key diagnostic question is not how long the answer takes, but whether the original point is ever actually, eventually reached.