Itīs probably correct that itīs the small size and popularity that makes it hard to find one.
It seems as there is a very limited amount of reward night rooms assigned also (one?) - and it would be nice to be able to figure that out before one starts to test.
(Like a first available reward night date shown or so something - and (less likely) the minimum/average designated reward rooms).
Still (after testing all dates individually for 2006) there was not ANY reward nights available until 24/12-30/12 2006 (exactly the last week possible to book - 50wk prelimit - that week just released for prebooking) which to me indicates that some tactic/game seems to be involved where some entity/individual(s) is routinely booking up this place for reward nights.