I don’t know if I can “prove” anything Art, but I would like to find out more about why some productions want nothing to do with YT content ID music. I think the issue is the potential for “take downs” by YT. If a production uses music that is enrolled in the YT Content ID Program, and the production ends up on YT or FB, there could be problems. Even if the production is not shown on YT or FB but has an exclusive license to use the music, that could be a problem too. The general feeling I get from the licensing community is that they don’t want to deal with Content ID music, period.
Libraries and publishers can still collect royalties according to the Identifyy FAQ, but not sync licensing fees. As they explain in the FAQ, Identifyy deals with the master recording side, not the writers/publishers side.
That’s about all I have been able to figure out. Hopefully someone with more knowledge and experience with the YT Content ID and sync licensing will chime in here.