Hey @geekgirl :) Great to see you here!
This is the case for OBEs - when the brain is mostly only partially aware; but, for grieving-hallucinations they also take place during the day (when individuals are fully awake and conscious). Neurologically speaking this is the main difference between them and dreams, a state in which all consciousness is practically inactive as a result of parts of the brain (e.g frontal lobe) and its connected regions being 'shut-down'.
Thank you for taking the time to comment :)