No, its not incorrect reporting, the "weathered bullet" is in the autopsy report (see attached document).
The weathered bullet is mentioned separately in the report, but without any further details provided. The autopsy does not discuss where it came from, its exact condition, it's caliber, if it was a pistol or rifle bullet, but I believe we can conclude it played no role in Suzanne's death. The word "weathered" indicates that it had been exposed to the outdoors for a considerable time, perhaps showing signs of rust or wear from soil or water, suggesting it may have been at the location for an extended period of time, collected as precautionary evidence, likely incidental debris from a rural, outdoor area where hunting or shooting activities are common. The report clearly states there were no signs of injuries occurring around the time of death, as verified through a specialized examination of the bones, and the death was ruled a homicide through unknown methods, but in the presence of intoxication from butorphanol, azaperone, and medetomidine. No gunshot wounds or related injuries were found on the skeletal remains, making it unlikely that the bullet was directly involved in Suzanne's death, IMO.