From whitepaper-
Apple ProRes 4444 fully supports 4:4:4 image sources, from either RGB or Y’CBCR color spaces. The fourth “4” means that Apple ProRes 4444 can also carry a unique alpha-channel sample for every pixel location. Apple ProRes 4444 is intended to support 4:4:4:4 RGB+Alpha sources exported from computer graphics applications such as Motion, as well as 4:4:4 video sources from high-end devices such as dual-link HDCAM-SR.
Never says it RGB or Y’CBCR :-/ can be both ?
Any codec can support both.. you just convert to it. What it actually is would be nice. Can it be either? :-/
s