It comes down to TRUST.
The reader TRUSTS the writer has used sources carefully and honestly.
It is drilled into the JW's mind that the Org. is trustworthy and truthful in all things, while 'the world' should be treated with suspicion because it is dishonest and deceptive. The Org. depends on its adherents buying into that claim.
It is only when there is a chink in that trust of the Org. that a JW will scrutinize what the Org. says and begin to see how unscrupulous the Org's writers really are - not just once or twice, but over and over and over again.
*** yb11 p. 9, 13 Highlights of the Past Year ***
The Writing Department follows the pattern of ‘tracing all things with accuracy.’ ...
... In summary, the Writing Department insists on using only material that is accurate and truthful, even regarding seemingly insignificant details. As a result, “the faithful and discreet slave” can consistently supply spiritual food that brings honor to “the God of truth,” Jehovah.—Ps. 31:5.
*** km 12/93 p. 1 par. 2 Set Aside Time for Magazine Activity ***
The Watchtower and Awake! are products of careful research
*** sg study 21 p. 110 par. 9 Informative Material, Clearly Presented ***
Accuracy of statement. Jehovah’s witnesses are an organization of truth. We should want to speak the truth and be absolutely accurate in every detail at all times. This should be so not only as regards doctrine but also in our quotations, what we say about others or how we represent them, also in matters involving scientific data or news events.
*** w81 2/15 p. 18, 19 Do We Need Help to Understand the Bible? ***
How shall we view the spiritual food provided by this “faithful and discreet slave”? Should it be viewed critically—‘Oh, well, it might be true but then again it might not be and so we have to scrutinize it very critically’? Some apparently have felt that way about it. To support their way of thinking they have quoted Acts 17:11 ...
... But does this mean that those Beroeans were looking for flaws in the message they were hearing, or that their attitude was one of doubting? Does this set a precedent for regarding critically the publications brought forth by the “faithful and discreet slave,” with a view to finding fault? Not at all! ...
... We can benefit from this consideration. If we have once established what instrument God is using as his “slave” to dispense spiritual food to his people, surely Jehovah is not pleased if we receive that food as though it might contain something harmful. We should have confidence in the channel God is using.
*** w67 6/1 p. 338 par. 12 Move Ahead with Jehovah’s Organization ***
We may think of study as hard work, as involving heavy research. But in Jehovah’s organization it is not necessary to spend a lot of time and energy in research, for there are brothers in the organization who are assigned to do that very thing, to help you who do not have so much time for this, these preparing the good material in The Watchtower and other publications of the Society.