Seems the most likely -- there was never a proper a survey, never any proper scientific or research teams sent to assess it. It was full of the stuff, I'd never seen anything like it, not just Covvie tech but others, too. Older. More powerful. Entire structures intact and functioning when most we usually see are ruins.

[ So it would be like, super bad for Cetaganda to get there, okay. ]

Chorus was real far on the fringe of colonized space, probably one of the last colonies founded before the onset of the war. UNSC went out a ways for it because of what was on it, and there was no wormhole collapse or anything, but as the war went on and even as it ended, the UNSC kind of -- forgot about it. Leaving the people there to govern themselves.