I'm not sure why you say so? To me that seems obviously literally just swapping/weighting between a set of predefined voices. I'm sure you've played a game with a face generator - it's the exact same thing, except with audio. I'd also observe in the demo that they explicitly avoided anything particularly creative, instead sticking within an extremely narrow domain very basic adjectives: neutral, dramatic, singing, robotic, etc. I'm sure it also has happy, sad, angry, mad, and so on available.

But if the system can create a flamboyantly homosexual Captain Picard with a lisp and slight stutter engaging in overt innuendo when stating, "Number one, Engage!" then I look forward to eating crow! But as the instructions were all conspicuously just "swap to pretrained voice [x,y,z]", I suspect crow will not be on the menu any time soon.