Preliminary statements: I am disinclined toward theories that remove Rose's moral culpability in whatever happened, since this has been so central in complicating our picture of Rose and Steven's relationship toward her. The "misled/lying" categories include "Pink Diamond wasn't actually shattered/was poofed by one person and shattered by another" and "it wasn't actually a sword," as well as "Rose didn't do it."
- Everyone who thinks Rose Quartz shattered Pink Diamond are wrong, but in good faith: misled, mind-wiped, something. This is dramatically unsatisfying and pretty hard to imagine working, too.
- Everyone is actively lying.
- The motivation of Eyeball!Ruby, who claims to be an eyewitness, to lie is difficult to discern. She claims to have specifically taken the mission to Earth in hopes of closure against Rose Quartz, and I don't see anything in her actions contradicting that or supplying another motivation. (Other Homeworld Gems might have reason to lie if it were an inside job, as Blue Zircon suggested.)
- The motivation of the Crystal Gems to lie is . . . almost unfathomable, because they know how much angst this is causing Steven. (Yes, even if they're protecting Pearl.)
- Eyeball!Ruby might be misled because of the inside-job thing, but the Crystal Gems lying runs into the same problem as above.
- Eyeball!Ruby lying has the same problem as above; the Crystal Gems being good-faith wrong requires Rose to have a motivation to lie to them. Possible reasons:
- Protecting someone not a Crystal Gem. (Who? A persistent fan theory is that Pink Diamond wanted out and worked with Rose to do so. This seems baroque and the only suggested reason why is that Pink Diamond also loved the Earth and its inhabitants; I think this is less plausible after "The Zoo.")
- Something else I can't think of.
- Rose shattered Pink Diamond, but a Homeworld Gem secretly betrayed Pink Diamond and helped Rose: Yellow Diamond, Pink Pearl, or White Diamond are obvious possibilities. Rose was then betrayed when the Diamonds unleashed the corruption on retreating from Earth.
- Rose shattered Pink Diamond, and our Pearl shape-shifted into Pink Pearl to make it possible (or Rose had some other help from the Crystal Gems).
- Rose shattered Pink Diamond, with assistance from someone not named above. This is dramatically unsatisfying.
- Rose did not shatter Pink Diamond, but she body-swapped with someone who did. (Subdivide this further into Rose knowing or not knowing that the person she was swapping with intended to shatter; refer to above for why Rose would have taken the blame; refer to above for possibilities as to who helped her.)
Yeah, I still think Rose did it. Options 4.1 and 4.2 are my choices.