Well as Joseph Staten himself said, "Newer games, if conflicting with the previous canon, become the currently established canon."
Anyway, why are you guys so stressed out over that tiniest of details? Has there ever been a moment in Halo lore where a passage or person has said "Flood forms don't need brains"?
Find that moment for me and I'll understand.
"This one has forgotten whether it's heatsink is over capacity. It wonders whether the criminal scum considers itself fortunate" ~ Blasto, the only Hanar Spectre.