It seems like there's no rhyme or reason for which retailer is going to fulfill their orders first.
What you mentioned about placing multiple orders isn't the first time I've heard this. It seems like a number of people in the collecting community are placing multiple orders for the same item. And when they get the first shipping notification for an item (like Paz Vizsla, for example), they will cancel the order with the retailer that hasn't sent a shipping notification.
Now, with Hasbro Pulse as well as Amazon and other big box retailers, I am less inclined to be sympathetic to them having more inventory on hand. But I do wonder if this might build up to an effect on future orders from these retailers because they wind up with a lot of cancellations. Could this practice be one of the contributing factors that brought down Dorkside Toys?