Since the protagonist is an Objective Story throughline character, it is natural that he would be involved with the story goal which is, structurally speaking, located in the same Type as the Objective Story Concern. This is particularly true in the software implementation of Dramatica.
The confusion seems to stem from the implication that the "Story Goal" can be something other than the same Type as the Objective Story Concern. The simple answer is "no," they must be one and the same (though the storytelling for each will be different).
Why then does the theory book say that the story goal will "be of the same nature as the Concern of ONE of the FOUR Domains?" I'll try to explain.
First of all, each of the throughlines has a Concern. Though it is not explicitly stated, the implication of the theory is that each of the four throughlines can have its own goal. This means the Overall Story throughline might have a goal, the Main Character throughline might have a goal, the Impact (Obstacle) character throughline might have a goal, and the MC v. IC (Subjective Story) throughline might have a goal.
Secondly, when you determine a Concern for one throughline, you effectively determine the Concerns for all four throughlines. Structurally speaking, the quad position of the concern in a given domain/throughline on the chart will be the same for all of the concerns. For example, if you choose "The Past" as one throughline's Concern, then you are also choosing "Memory," "Understanding," and "Conceptualizing" for the other Concerns. That is why we wrote that the story goal will "be of the same nature" as the other Concerns.
What, then would be the "Story" goal?
In general terms, the Overall (Objective) Story throughline "goal" is most akin to the traditional, non-Dramatica definition of Goal. When examining specific individual works, however, the Overall Story throughline is often NOT the most emphasized throughline and therefore doesn't necessarily have the greatest prominence in the storytelling. In such a story, the "goal" of the most emphasized throughline may appear to be the "Story Goal."
So, the confusion grows out of two standards of reference when defining "Story Goal." If you use the "traditional" definition, then the Overall Story Concern will be the same as the Story Goal. If you base the definition on the throughline with the greatest emphasis, then ONE of any of the throughline Concerns would be the Story Goal if it is in the throughline with the greatest emphasis.
Which point of reference is right? If your working with the Dramatica software, then the Story Goal will always be the same Type as that of the Objective (Overall) Story Concern. The other point of reference is helpful in understanding why the goal that seems to be most important in the "story" may not be tied to the efforts of the protagonist, antagonist, and other characters' efforts in the Overall Story throughline.