With that said, the pinout for where the carrier board is not a secret. The Nvidia Jetson modules just plug in without a carrier board. The CM4 takes a carrier board. So you could create a carrier board for the Turing Pi for almost anything you wanted. How you get the capability from the module to carrier and thus to the Turing Pi v2 is all on you.
If you meant the CM3, the reason why they aren't producing a carrier board probably comes down to R&D. They would need to design it, support it and they already sold a product that uses the CM3. For where they are going with the Turing Pi v2, the use of CM3's would low and doesn't really fit with the rest of the modules you can/could use.