The 1985 incident occurred in South Africa, where it marked the beginning of a notorious spate of such murders; hundreds of people were being killed every month across the country, several of them the victims of necklacing. Significantly, the story of the first person thought to be the victim of necklacing in South Africa is quite well documented; Maki Skhosana was killed in July 1985, the death was recorded by the media at the time in graphic detail, and her sister gave detailed testimony to the Truth and Reconciliation Commission in 1997 about the incident (you can read that testimony here - some graphic details of the violence are described). Her death, and those that followed, were very disturbing to observers at the time, and remain very poignant memories of apartheid and the violent excesses it led to on both sides of the divide.

With Gandhi's death and the incident in South Africa being so close in time, if necklacing was being practised in India first, then this has probably been glossed over because the necklacing attacks themselves are not as richly document or remembered in the Indian context, whereas they stand out in South African history as one of the most well-known and disturbing characteristics of the unrest of the mid-1980s. Whilst there are specialists who look at both India and Africa, comparative history tends by necessity to be more concerned with underlying themes and movements rather than nuanced detail of specific incidents, and this is the kind of thing that might easily go unnoticed unless someone was researching a fairly precise topic.