Blu-ray/DVD Combo Discs

[viiv]

Right in the first few pages of my Sony S300 manual (you can pull it off the esupport website in PDF if you want to see it), there is specific mention of "types of discs this unit can play" to Blu-ray/DVD combo discs, ala the HD DVD/DVD combo discs. So that means there are provisions in the format for this. Now where are they?

I know in Wikipedia there is mention of a JVC combo prototype with a third DVD layer, but the Sony manual which is printed right from the horses mouth in Japan, would not be mentioning hypothetical possible prototypes, only hard facts. So once again, why is there mention of them in the manual and where are they?

Edit: I specifically hoping for single sided triple layer discs as mentioned in Wikipedia, NOT the ugly double sided discs. I have not seen any evidence that these would be double sided.