Strictly speaking yes, we can't be certain how much the Xbox contributes to Microsoft's EDD because they keep moving various other devices in and out of it (Zune, Skype, Windows Phone etc)
Same was said for Sony for the past 4 years as Playstation was lumped into an even bigger company segment which changed at least once in the 4 years too. Even before (and again now) when it was the "Game" segment we have problems. Sony is a much bigger company than Nintendo and therefore don't give as much break-down between platforms as Nintendo does. It's also possible that some aspects that are required by the Game segment are not included within that division and therefore don't impact on any profits/loss made (for example the current game segment doesn't include disc production)
As such... when Sony has a dedicated "Game" segment it's easier to figure out profits/loss of playstation brand as a whole than it is for the Xbox brand, but still easier to estimate Xbox 360 profits/loss than it is for a specific PS platform (at least while MS only supports 1 platform)
Nintendo at least is easy to figure out. The only other thing they do is Hanafuda cards, which make up maybe 1% of the revenue if that.
