And companies ship the same proportion as the other since when? What if both companies always shipped 10,000 more than they needed? The fact is we don't really know - except that Sony hasn't been able to ship enough for much of the year (under control now)
Companies can't just keep shipping more than they sell every quarter. Retailers can refuse shipments, and in fact for as many quarters that they ship more than they sell, there are just as many quarters where they sell more than they ship. It is just like inventory levels in any other business, oil for example. Sometimes it goes up, sometimes it goes down.