There will be some cases where you never do. Yet you still have an on-site stay.
See this example, which I know I have done time and time again, and can't be the only one
For instance, say I start out with a 5 day stay BWI. Then I book my flights much later and end up flying in a day earlier. Due to the quirks in the Disney booking system I can't add on to my BWI stay so I have to book a separate 1 day stay at BWI in a different room category but I keep looking to change my original reservation to a 6 day stay. In the meantime, I book FP for the 1 night stay, of course. Eventually, I do get my 5 day stay changed to a 6 day stay so I cancel my 1 night stay. What happens to my 1 day worth of FP? No new stay is booked. The stay for those exact FP has been canceled. Does
MDE see there is still A stay booked for those nights?