Just tried with a dummy reservation at the end of May - please beware that the three hotels in the vicinity of the airport do not allow booking rooms for day use (altogether, nothing until EOY).

In Royal Rose Abu Dhabi the day use is 9am to 6pm while in Conrad Abu Dhabi Etihad Towers the day use is 10am to 4pm - when you start the booking process, these times are clearly stipulated.

If I remember well from COVID times, you will get points for your spending but no night / stay credit - but please verify this with HH, just open a chat and ask an agent.