My Lear 60 (EROS mask) cabin fire checklist memory items are worded exactly the same as yours. The systems description states that 100% mode supplies oxygen only when demanded unless the cabin altitude reaches 37,000 ft, in which case positive mask pressure will be maintained. In EMER mode, 100% oxygen is supplied under a slight positive pressure at all times, thus preventing smoke ingress.
I guess doing what the checklist says is okay for checkrides and up until you get real smoke in your mask. Then maybe it's time to exercise some initiative! I'd rather train for how I'll REALLY do it though.