AI turns the lights on regardless of behaviour mode (stealth, aware, combat etc.).
It happens only when AI is a gunner, having AI on passenger seat makes them not to switch lights.
It happens to AI driver as well. When AI driver gets out, the gunner AI turns the lights on, even in stealth or combat mode. Telling the AI driver to get in, causes him to turn the lights off as soon as he mounts driver's seat.
This behaviour happens even with NVGs equipped.
Like if the gunner was afraid of darkness :)