8-bit RGB with dithering has less banding than 10-bit (which suffers from YCbCr420 subsampling as well) on the LG OLEDs. You don't need a 10-bit signal or a true 10-bit panel for HDR because the quantization noise from 8-bit + dithering is invisible. Many HDR panels are 8-bit + FRC, so you might as well do 8-bit RGB + dithering at the source instead of outputting an inferior 10-bit YCbCr420 signal.