When that elder giving testimony tells the court that people have claimed disfellowshipping was "the greatest thing that could happen to them," I don't think he's lying. But we do have to understand what might be going on here.
Remember the Stockholm Syndrome? The one where the captives develop a close bond to their captors? I think this situation triggers this feeling in the disfellowshipped person. They're being held hostage by the WTS's cold disfellowshipping policy. When the announcement occurs, it's like a gun held to the head. At first they are scared, upset, and despondent, just like a real hostage. The society tells them what they have to do to get out of the bad situation: "Just keep going to meetings for at least six months--don't miss a single one--and thenwe might let you talk to your family and friends again if you're sorry."
In time, like the hostage, they begin to adapt to their situation. They get used to the chains; they have to if they want to get out of the problem. Then the elders let them go as hostages, and what happens next? The person loves the organization more than before! It's a perfect recreation of the Stockholm Syndrome. It's the Society's most powerful tool in keeping the r&f in line.