I wouldn't call it a relaxed patrol though. It seems more a case of "find the cyborg".

: It's a big room full of crates and combat vehicles, and there's a wide
: passage that connects it to the grav lift room. I don't think the game
: explicitly says what it is, but I've always thought of it as one, and I've
: heard other people refer to it as such.

I've just checked the T&R transcript on halopedia and the game indeed doesn't say 'cargo bay'. The site itself uses that term for the boarding room and then refers to the second room as "another cargo bay", but your use makes better sense. I'll have a think about whether to adopt it on my site, as it does seem more appealing than 'second room'.