"No blackouts" does not mean there will always be awards available. "Capacity controlled" just means there is a limited number of seats. Unlike other airlines which have a cheaper limited awards and expensive unlimited awards, Hawaiian only has the limited kind. Flex awards are not unlimited, they are just another category that becomes available once the savers are gone. Once the Flex awards are gone, no more award bookings for that flight. Obviously around the holidays, awards go quickly. Are you sure there were never any awards available for the dates you're looking at?