Unavailable Calendar dates show as available for guests who want to change reservations. Why?

[Shaun-And-Tracy0]

I have the setting turned on that blocks off the day before and after bookings.  The problem is when guests want to try and change their reservation those dates show as bookable for them on the calendar even though it would show as blocked off for a new reservation. 

Why is that? I've only been hosting a month and have twice had to explain to a guest why I am denying their booking change request as the date they are trying to add is blocked for cleaning.

Why doesn't airbnb keep these blocked for all calendars? Unavailable means unavailable. 

[Mike-And-Jane0]

@Shaun-And-Tracy0 It depends on the situation. If the guest books for a week then the day after is blocked for cleaning. As long as the subsequent week is available then the guest extending over the blocked day would be fine and a new day will be blocked. If you really want to absolutely block the day after a stay (perhaps because you have booked a cleaner) then manually block it and it will be unavailable to existing guests.