This is fairly typical for properties in locations where overseas flights tend to arrive in the early morning. Properties tend to view the early check-in as a discounted concession to what was historically the practice of booking the room for the night before.

As you can see, even this property only provides the service on a space available basis. If you want to guarantee a room, you will need to book it for the night before (and then make certain that the property knows that you will not be arriving until 8:00 AM).