I remember asking this question to couple of elders who came to visit me. I had pointed out their failed prophecies, and the fact that they were constantly making corrections in their publications, and how this proved god wasn't really behind it.
They went into the usual song and dance about how the GB were simply imperfect men, and never claimed to be infallible. I reminded them that the bible writers were also imperfect men, and yet the bible supposedly was infallible. Why? Because god's spirit was behind it. If god's spirit were really behind the organization, than why wasn't it infallible as well? Why the constant corrections?
They responded that, yes, the organization was spirit-directed, but they weren't inspired as the bible writers were. It was a genuine WTF? moment for me.
It seems like nothing more than a grammatical loophole, to give them an out, when and if their prophecies fail, or when and if they receive "new light", and need to make a correction on a doctrinal matter.