I'm pretty sure in the time I have been playing FS, I know just a meagre 6 years, that the Christmas Special Offer delivered chests and fsp prior to the Christmas double XP event. As the Christmas Double XP event has never been this early in the month.
With this being the case I'm at a loss to understand why there would be a problem in changing the delivery date of the Christmas Special Offer goodies so it coincided with the XP event. And yes, there is a "deilvery date" for the Christmas Special Offer so it can be sent as gifts to others but I would imagine that most would want to receive this gift prior to an XP event so they can use the goodies during it.
For the disgruntled; I fully understand your dismay. I would be rather annoyed, annoyed being quite the understatement, if I had purchased the Christmas Offer only to later find out, which is the case, that the Double XP event will be done and dusted prior to Chest or Chests and FSP delivery. I mean for me it would be one of the prime reasons for purchasing the Christmas Offer....that being to assist in leveling in the XP event. So, is there any point in me purchasing the Christmas Offer knowing what I know now? Not really.