Back in "Bismuth," Bismuth revealed that she designed Rose's signature blade so that it could only poof enemy gems, not shatter them. That was one of the points of contention between Bismuth and Rose, after all. Yet, according to Blue Diamond, everyone knows that Rose shattered Pink with her sword. It's not brought up in this episode, but it does add to Blue Zircon's argument that what everyone "Knows" happened isn't necessarily the truth. This is later proven correct in "A Single Pale Rose."
Defense Zircon's case relies on a bit of this in the official story of Pink Diamond's death- how could Rose Quartz, a well-known and wanted criminal, get close enough to use a melee attack to kill Pink Diamond without anyone in her entourage noticing (Rose was the only Rose Quartz around at this point, since all the others had been eliminated from Pink Diamond's guard, so there was no chance of her being mistaken for someone else or using something like a Bavarian Fire Drill) and attempting to defend their Diamond (like her elite Agate guards) or at least warning her (like her Pearl, who would be close to her, or her Sapphires, who could see the future)? Zircon's answer is that it was an inside job- the real killer was someone who Pink Diamond knew and trusted, who could approach the palanquin without being seen as a threat.