I don't think LSW leaked it, but he certainly knew it was going to be seen by his friends in the establishment so there's not much difference. I agree with the views that his non-apology of a letter was amateurish in the legal sense, but that suggests he
1) either had bad or little legal advice
2) refused legal advice from his mum and friends
I believe it was the latter, a decision as a combination of indignation of the system (that his grandfather created) and a belief that he has nothing much to lose by going on self-exile. The thing is, I wonder if it has shaken the resolve of LHY and his wife to pursue the Oxley matter, knowing their children's every word are being examined by the establishment.
The AGC, by pursuing this case, only helps to cement LSW's views on the judiciary for being litigious in the eyes of foreign news agencies. If they didn't pursue this, they lose legitimacy in the eyes of the people calling for LSW's blood. It's a lose-lose situation for them.