That would be admitting to one mistake, it's true.
Would that make everything okay? What about blood transfusion martyrs? And the 2-witness rule? For example.
In addition, if they admit to being wrong, what does that say about being directed by g-d's holy spirit? Is he toying with them (us), or are they false prophets? Why do g-d's spokespeople keep getting these end-of-days dates wrong?
Those could be thought-provoking questions, if I were still a JW. Questions that could give the GB and their overlords pause. Admit to one flaw, and the downfall of the Tower could be imminent.