What has my curiosity piqued with the ME in this case is how broad his range is--I believe that it is anywhere from 10 days to 6 weeks. In my experience, I have never come across an ME opinion with such a broad range when the body is found within four weeks of disappearance.
That is why they use entomologist's in some cases. They can pinpoint the time of death closer to the actual time.
Medical examiners can give a pretty accurate time of death if they get to the body soon after death. But if it has been quite awhile before they discover the body they tend to give a wide range of time for death.