When New Zealand and Australia changed their law such that the salary of their Governors General became taxable, they essentially just increased the level to offset the fact that it was grossed up. They have different traditions in terms of how they set the salary of the Governor General. In terms of when those decisions were made, it was quite clear in the literature we reviewed that the decision was to just gross it up so that the net after-tax benefit was the same.
On May 15th, 2012. See this statement in context.