Well, I feel slightly more thorough, if that was scripted to spawn; funny that I'd botched the stealth twice, and tried to run, but the enemies felt ALL BUT OMNISCIENT after that. I think once Lara's spotted, she doesn't become unspotted; though the Cultists' dialog implies they have lost her, they were busy implying they'd lost me, while still firing on Lara's location, though she was in cover behind an outcropping of rock.
It was a great area, but it exposed some AI shortcomings, or at least what the AI could express vs. what it was actually doing.