Is there a traceable sequence of events that led to the change, a credible timeline? For example certain governments were starting to ask questions about the subject, in a similar way that the Norwegian government began to ask questions about the shunning of children?
I would assume that an external paper trail wouldn't exist because if the legal department became aware of any government interest that could result in negative impact if not addressed, and they were sensible, they would be advising the GB to change the rules post haste. That assumes rational thinking.
On other threads people have suggested that the GB and other Bethelites really believe the "God's chosen people" thing, and that God will protect their way of life and how they do things, so it is possible that the Norway thing took them by surprise.
Is the shunning policy more important to them than the whole military/civilian service issue was?