1. (Not necessary, but recommended) Adjust a character's skin color via CC4 Modify > Skin > Activate Editor > Skin Base > Base Color> Brightness
2. Export as follows FBX > Clothed Character > C4D R19+. I left textures embedded, pose unimportant.
3. Open FBX in C4D (I'm using R.21.207)
4. Character's eyebrow material should show up without alpha channel, as seen in attached photo.
5. Open material for Female_Brow_Base_Transparency. The transparency file, instead of being associated with the alpha channel, will be in the transparency channel instead.

So far, I've only seen it affect this material. Everything else exports/imports with the alpha .PNG properly in the alpha channel.