The issue is not that he was convicted as a minor, but that he was mistreated during incarceration.  The laws regarding how children are to be treated were violated, and the Canadian government participated in it.

I don't like this either, but we are a land of laws and as bad as it stinks to pay this guy, a settlement was necessary.

Now hopefully the widow of the soldier he killed will be successful in her efforts to get this money from him.