Not only must you not know what happened, you’re not even allowed to ask what happened.
Sadly, that's not unique to the upper echelons of the JWs. Lots of major corporations operate that way these days. Also, remember all the fuss a few years ago about a certain footballer's sex life and him taking out a "super injunction"? They've been used in corporate and celebrity privacy deals, and because you can't even discuss them without risking prosecution, they are a particular threat to an open society, although by their very nature it's hard to know how often they have been used.
It seems to be a product of a paranoid society, and it's not surprising that the GB would also increasingly fall into that category. Any group that is not willing to let light shine on their activities or to even have them debated (let alone questioned) is liable to fall back on draconian secrecy measures if it can get away with it. That's true of corporations, governments or religions.
I wonder if even the people who made the “don’t ask” rule know what happened themselves. Or are they passing on a “no ask” policy from above without being informed what the situation is about.
I suspect most are the latter group. We know how the hierarchy works. The word comes down from the GB, to branches, to COs, to bodies of elders. So most of those layers probably don't even know the details themselves, they just absorb the "don't tell, don't speculate" message and pass it on.