> The suspected detection stems from an excess of infrared emission from a dust blob near the compact object’s predicted position.
[1] https://arxiv.org/pdf/2004.06078.pdf
It didn't go supernova in 1987. It happened around 168,000 years before that, but it took the light from the event that long to reach us. A better title might be "A supernova was observed in 1987".
I have a philosophical distaste for defining reality as something we can never experience - the condition of anything at a distance.