Found this buried in the Maxon FAQ page:
https://support.maxon.net/hc/en-us/articles/9057076364572-Why-is-the-CV-Toolbox-not-showing-up-under-my-Extensions-menu-after-updating-to-Cinema-4D-2023-2-and-later-

My guess is that it's similar to their answer on the Toon shader: The developer that originally made it is no longer there and nobody knows anything about it (how its written, etc)