In addition to not wanting the financial obligations, as well as not wanting to acknowledge any problem with their policies, the GB also might think that publicly joining such a scheme (that primarily involves other religious organisations) may be perceived as a form of ‘interfaith’.
I suspect that it won’t be specifically covered on their website because that is not easily achieved without drawing attention to their mishandling of abuse cases. But the site might generically bundle Australia in among ‘lands’ where JWs face ‘persecution’.