This person has no mental deficiencies (that I know of ), other than thinking it's OK to take tax payer money when you can physically work...
The issue for them not working is physical in nature. Problem is this same supposed injury does not stop them physically in sporting activities and physically working for cash. My take is if you can participate in sporting activity and work on the side you should not be on welfare...Even if the injury DID prevent them from being physical they could get a low physical impact job...
I looked at this web page re reporting:
https://www.centrelink.gov.au/wps/portal/clk_common/TORS
Where it details they need a lot of confirming info (name, birth date, address etc..). Seems by comments it is OK just to ring up with maybe not as much info?
Definitely report by a phone call.
Phoning up is much easier and they, in my experience, take it pretty seriously. I think that information is there to stop people making malicious reports.