It doesn't make any sense to me, either. Does any of you know the exact reason why the Region 2 release contains only one disc? I'm curious about why there's two different versions. I think that's a crumby arrangement.
Marketing decision, no doubt. Titaniacs aren't too thick on the ground on this side of the pond, so maybe they figured a slightly cheaper package would sell better and the extended version of the film itself would not be missed. As far as I can see the extras which were on disc 2 have survived intact and now occupy the vacated space on disc 1.
No doubt the accountants also decided that only the Japanese, who have a fondness for gadgetry, would want to buy the 3D edition.
Ah, I see. Well, at least the extra features were left intact. It is a shame you don't get to watch the extended version of the film though. You said this package is slightly cheaper. How much does it cost? My two-disc set only cost $19.99, a cheap price compared to most DVD releases boasting extended editions.