Another explanation for advanced decomposition could be that death occured earlier than assumed.
As for the identification, this might hint at foul play. I've seen other cases where police couldn't rule out involvement of family members and after finding the body couldn't ask them to identify the body since it would have given hints about the cause of death; knowledge about that would help identify the perpetrator, so they want to keep it under wraps. Sometimes they would ask for identification of clothing.
But of course there are dozens of other explanations.
Thanks for explaining that for me!!!