According to the article referenced above (assuming it’s accurate), the officer notification was instituted towards the end of the Vietnam war.
In another note, I recently watched a program about a Marine Reserve unit that took substantial losses in Iraq. Concerning the death on one marine, his dad was home when the officer came to notify. His wife (the marine’s mom) was out shopping. The father didn’t think he could bear to tell her, so he asked the officer to stay until she returned. He also asked that they move their van so she would not be tipped off before coming in to the house. The officer complied with both wishes.
Performing funeral details, as an active-duty staff member of a Marine Corps Reserve unit, remains one of the hardest, yet most honorable and fulfilling tasks I performed in a 20+ year military career.