You know you are in trouble where your source of BD interactivity data continues to come from us .
Anyway, the requirements could be infinite but as long it is missing in action in real players/products, studios can't target it . And no spec can insert a secondary video decoder in the products people have bought without it. So this leaves the studios with a tough situation of creating discs which leave some segment of the market behind, and open themselves up to having returned discs from those customers. Or worse yet , having liability cases to deal with.
Even more puzzling is why PS3 is behind in implementing it. Since it has the lion share of BD players, you would think if it had full support, some studios would target it. So either the PS3 lacks the functionality, or having partial support in the installed base is not good enough for the studios.
Either way, this is one hell of a mess for BD format. The screaming behind the scenes is even louder than what you read in the press. Had BD come clean 2+ years ago when this decision was made, folks would be less happy than they are now. As I said before, "Tell it all, tell it now." Folks thought they were pretty smart keeping this data from you. But once it gets out after the fact, the damage is even bigger