So, I’m trying to blast my way through a ton of books before infinite comes out, And I’m reading how there are humans in the Keepers of the One Freedom. And I wouldn’t really even make a big deal about that since space is big and all but, technically Halo: Discovery Outpost was actually suppose to be like Cannon right? That ONI and the UNSC was declassifying stuff about alot of stuff done during the covenant war and what the Halos actually are. So, if they were declassifying (almost) everything, then why would humans, even colonists, still believe the halos would do anything but kill them? It’s not like they would join the Keepers just to get back at the UNSC, there are other ways to do that. Or…did they just not think about that when writing the books? (I’m guessing the latter)
No sane government would ever think it right to just start declassifying incredibly important and incredibly dangerous stuff such as the Halos, ESPECIALLY in a setting where civilian space traffic is free to move around without restriction or oversight from said government. Given how focused the UNSC was on propaganda and keeping the civilian populations in the dark about how badly the war was actually going, I cannot see them going around and declassifying all of this information as anything other than extremely bad and inconsistent writing.
As far as we know, it’s not something the public would know about because ONI locks anything that even resembles Forerunner technology down that the UNSC finds.
But one could argue that after the events of Halo 5, that could be no longer the case.
Most likely no, the Unified Earth Government does withhold information from the civilian population like the flood’s existence.