Is it unusual for a M.E. to enumerate the exact of destruction as unknown?

Is it unusual for a M.E. to enumerate the exact of destruction as unknown?
No it is not because our bodies are so complex and begin to break down the moment we leave behind making it difficult to determine cause of disappearance in rather a few cases. It can also be that there are more than one competing cause where it can't be distinguished as within a suicide/homicide/accidental death shield. However the main cause of undetermined death is when a individual has have work done by EMS or Doctors that have muddled up the inspired cause due to treatment and medication given. I hope this helps you out rather.
no
if someone's body has be through a lot of perimortem trauma, it might be difficult to identify what among the evidence be actually the produce of death.