Daithi; Not if Amazon is selling more. If eInk could only produce 40k 6" screens in January (Pulling these numbers completely out of the air) and they had demand for 50k (15k from Amazon, 10k from Sony, 25k from the remaining lot) they would most likely ship 80% of each order. If Amazon was maintaining 90% turnaround in a month versus 75% for Sony/others then you could easily wind up with Kindles backordered while Sonys are sitting on the shelf, while still being a supply side issue.
Mind you I'm just giving an example, it could entirely be as you say... Or Kindle gnomes broke into the factory and changed the shipping on half the orders to their underground lair. Who knows?
-MJ