I'm a consultant and operate in this same type of environment, albeit IT, not watchmaking. We build custom software for our clients and we do so by charging for our time and building based on their specifications. In the end, the final product belongs entirely to the client, not to my company and certainly not to me. I understand Christian would have retained some knowledge, but unless there was a specific contract setup to grant him intellectual rights to the movement design (which I doubt, since LVMH used it in other watches), then at best he could say he worked on the movement design, not that he had any ownership rights to it - intellectual or otherwise.