Fine, but that doesn't change my basic point. Why bother with an auction that will necessarily get less than an open market?
The same reason you wholesale anything; You get a transaction that moves a large volume quickly. Basically all consumer goods you buy in any kind of branded store works this way, Wholesalers, whether manufacturers or a middleman, sell large volume to companies who then take the burden of distribution but reap the benefits of charging retail price and profiting on the difference between that and the wholesale cost plus infrastructure/logistics costs. The wholesaler gets the benefit of moving a large volume at an agreed upon price and not having to worry about inventory control, distribution, or logistics of getting it to the consumer.
This is not strange, or even strange at all. Side benefit in this case, they get the auction entry fee from everyone bidding regardless of whether they win and also a look into who is interested in amassing a large quantity of bitcoins.
Honestly this shouldn't require explanation,