Apparently, only they are allowed to quote and make hay out of anything earlier than last month.
They don't seem to be very clear about their own teachings. It seems like it is becoming more common these days that they are personally rejecting ideas in older articles if they cannot reconcile with them. Maybe a better position would be to have them back up any views that they express by asking for a scripture to support it. As you point out, they can't do this.
I wonder if this is a new problem that is arising amongst the Witnesses but it seems that instead of being fully aware that they cannot answer a question, they immediately deal with this CD by feeling they are being persecuted or that Satan is just trying to shake their faith. You become the problem, not them.
A few decades ago, JWs had complete confidence that they had the truth, that they could answer any question put to them and they were right. The difference is, back then, it was very rare for JWs to be confronted with difficult questions. Most of the questions they would be confronted with were dealt with in their publications and could be researched if they could not recall something instantly but not the ones that we are asking today.
The organization has left them high and dry. They are expected to deal with the issues on their own. This is evident when Splane came up with a scripture that he thought supported the 'generation' teaching and told his sheep to meditate and come up with their own scripture to support it. Maybe the real persecution is coming from their leaders by way of undefendable doctrines.
It's amazing that they find themselves in such a difficult position when they have a huge resource available to them, one that they never had a few decades ago - JW org.
It becomes more and more evident why the message these days is one of obedience.