According the page you linked, a birth certificate and bank statement (or even a 'Document issued by <SNIP> or registered corporations.') would be enough. So if I get your birth certificate and have an Australian corporation, I can issue a letter saying you're a customer for a year. So I have 100 points and can pretend to be you?
That doesn't seem secure at all. The birth certificate has no photo (or, if it does, it won't be useful except to determine ethnicity), and the document from a registered corporation can be trivially faked.