I am confused as to why you think that's confusing. This is a pretty typical cancellation policy which ranges from 2pm-4pm. Resorts can sometimes have 72 hour cancellation. It usually matches up with check-in time but not always. The hard part is figuring out the time locally.

FYI when cancelling award stays last minute double check that the points get put put back into your account. CS is more than happy to cancel your reservation at anytime (even last minute) but the hotel sometimes keeps the points without warning. Just because they will cancel it does not mean you get your points back so always double check.