: The quote in the title seems to contradict the intro cutscene of Delta Halo:
: "I want all the information you've got on the first Halo. Schematics,
: topography, whatever. I don't care if I have the clearance or not."

: Surely Cortana briefed Keyes on the likelihood of running into the Flood
: (especially when assaulting the Library) - and if she didn't, surely
: Johnson might have mentioned it?

: Seems bizarre to have that information withheld that would've saved marine
: lives (e.g. by arming all of them with shotguns instead of BRs, SMGs and
: magnums)

We know that the Flood were released by the Covenant in Halo 1 by mistake. However, if we assume that "the rings work the same way" then the Flood should be contained and neither side would intentionally release the Flood knowing now what they were capable of.

Except the Flood weren't contained on Delta Halo.

They were already out and around. So the marines in Sacred Icon wouldn't be expecting the Flood, even if they were briefed on the entirety of what happened on Alpha Halo. It was also very foggy and hard to see, it's very possible the marines saw what looked like Elites running around, called Keyes, then called back when they realized their mistake and cried out "Not Covenant!" in panic.

It never really seemed out of place to me. I just assumed they weren't 100% sure that what they were shooting at was the Flood and that's why they worded it like that.