Except he wasn't wrong; he was right. The point is that once he is right, it doesn't matter if he has knowledge or not. Knowledge doesn't do anything which true belief doesn't do quite a well.
All that you have stated is that false belief is not as useful as true belief (and by extension, justified true belief), but so what? Did anyone say otherwise?
One question. Do you think it is easier to stand by your true belief if you have a rational argument to support it, rather than if it is simply a castle in the air?
For example, do you think it is easier for me to be confident in my belief that if I take I-94 to Chicago, I will arrive there if I have studied the map and based on that see reasons to believe that 94 leads to Chicago, rather than if someone I dont know told me that if I take 94 I will end up in Chicago, and for some strange reason I believe in this?
In essence, I do agree that what is useful is the true belief in itself, not the process of reasoning that we have used to support such a belief. However, it is much easier to hold on to a belief that you have supported with argument than to a belief that you have not supported with argument.
Thus, if the utility is knowledge in itself, our goal should be to hold on to this knowledge, supporing what we know with rational argument helps us to remain in tune with our true beliefs. Thus, the reasoning process that we use to support our beliefs is not an end in itself, but means to an end.
Suppose that before time t Bluewing believes P is true, and after t Bluewing knows P is true. Why is P more reliable after t?
Would P let Bluewing down before t? Would P feel obliged to be more reliable after t? What does the history of Bluewing's subjective experiences have to do with P (supposing P is not about his experiences)? And why would those experiences be important?
This goes back to our earlier example concerning economical predictions.
Suppose an economist has a formula to predict that there wil be a depression in China at 2040. Today he can say that he knows this because he has good reasons to believe in this. At 2041, he could say he knows it better as he has more and better reasons to believe that a depression would occur in 2040 in China.
Thus knowledge is to be equated with propositions that could allow a rational person to be confident in his beliefs. On this note, a blind guess should not be considered knowledge because it does not offer a rational person a reason to believe in the proposition we have in mind.
Therefore the term justified true belief is inseparable from the term knowledge, they are synonymous.