I came at the same information from the CDC which is more user friendly with descriptions, IMO.
Idaho - Coroner/ME Laws | CDC
I have a family member certified and trained as a Medicolegal Death Investigator. One of the first things they are taught when they go for that training is if you want to get away with murder, do it in a state where coroners are elected. In Idaho the coroner is elected. Requirements are US Citizen, at least 21 years old, resides in the county where they are elected, and will go to training in the future. That is it. No prior medical training required.
I don't see anything wrong with what the coroner did here. There are 3 situations that require investigation.
Stillborn baby, No.
Apparent violence/suicide/homicide. No, not apparent.
Suspicious or unknown circumstances. TD died at home in bed, that is known. Suspicious? In hindsight, sure.
The coroner's duty for a death not attended by or certified by a physician is only to report it to the Sheriff, which was clearly done here. Had TD died in a state with a Medical Examiner's office instead of a coroner system the autopsy would have been required by law.