@David-and-Annie0
I think it really depends..... I host only international guests and mostly longer-stays. I also never have same day check out/check in. If the request was because of flight times, I'd allow it without much thought.
I understand not all hosts are able to allow this, but if one knows WHY the guest needs an early check in /late check out, then it would be easier to decide whether to allow or suggest alternatives the guest could consider.
As a frequent traveler myself, if the check out time is noon, but flight is 8pm and there isn't much one can do with 3~4 extra hours with luggage, my first thought would be to ask for a *complimentary (=free)* late check out or free luggage storage. If there aren't free options, next I'd look at options that cost money and decide what works best, all things considered.
Asking in advance and being specific about times makes it seem like the guest just wants to know what options are available. I wouldn't want to be stuck in the middle of a trip with nowhere to go for 4hrs.