Think about it. A pre-order is a guarantee of a future transaction. It would be remiss for Amazon to offer pre-orders for items it won’t legally be able to sell when they eventually become available. It would also be remiss for Amazon to stock millions of dollars worth of inventory it won’t legally be able to sell in the near future and would have to return at great expense. The moment Amazon realized negotiations were breaking down (as their press release recently intimated), they had to reduce their exposure to Hachette inventory. That means reducing future sales, which is what pre-orders and predicted warehouse quantities represent.
These moves by Amazon might be less about spite and more about pragmatism. Even legality. That book you pre-ordered from us two months ago? We no longer have a sales relationship with that manufacturer. Here’s your refund.