It appears to be a TIR prism in the single chip laser DLP, it's a corrective lens more than it is a typical optical prism.
It balances and focuses the light uniformity, but does not appear to have anything to do with color splitting.
In a 3-chip DLP it uses an optical color-splitting prism known as a dichroic/trichroic prism (or multiple dichroics maybe). Prisms do not necessarily split color wavelengths, the design is such as they are splitting something in the light, but not necessarily always the color. From some googling, it appears the "industry term" of the standard color-splitting prism called a Philips prism, I'm guessing because Philips polished the design.
From my basic understanding of lenses from what I've read, I believe the TIR prism is more like a lens than a standard optical prism.
The only reason they call it a prism is likely due to the shape and amplitude and light altering characteristics, but it really sounds more like a lens.
BTW, the reason the color splitting cube is still a type of prism is because there are glass elements inside there that are prism shaped that disperse and split the colors, it's just hard to tell from the above picture, but the color splitting is actually made up of complex inner glass shapes.