The report that the police filed initially was in August, before Gary was found.
MSM report 28th August
"Police have filed a report with the coroner, declaring the disappearance of a Sydney man in the Blue Mountains a suspected death."
http://www.abc.net.au/news/2013-08-...-in-nsw-blue-mountains-a-suspected-de/4919586
MSM report 2nd September
"Police have reached a body in the Blue Mountains and confirmed it matches the description of missing Sydney man Gary Tweddle."
http://www.smh.com.au/nsw/gary-tweddles-body-found-police-believe-20130902-2t0vl.html#ixzz2m0aIbiZG
I would think that their report to the Coroner would have to be revised and re-filed due to the change of circumstances. Gary wasn't "missing" any more, he was now "found deceased".
Additionally, the post mortem report was required by the Coroner as Gary was now located.
The fact that these 'new' documents have not yet been filed, almost 3 months after Gary was found, says to me that police could still be trying to piece together a plausible reason/scenario why Gary was found down that particular part of Sublime Point.
If the Coroner is not happy with the results of the police investigation, he/she can just turn around and say 'go and investigate further'. If the Coroner feels that the police have done all they can do, then there is a good chance there will be a definite finding or an 'open' finding by the Coroner.
So, I guess, the police have to make sure they have done all they can do to come up with an answer as to how/why Gary died - and maybe they haven't completed that process yet.
http://www.judcom.nsw.gov.au/publications/benchbks/local/coronial_matters.html