That is a big part of it. Even if a little hum got into your unshielded interconnects from CDP, that signal isn't increasing 40-70db once it gets to the destination, so it likely is entirely unnoticed. But also because of the nature of things it's unlikely to pick up a bunch of hum to begin with.
Imagine this, your phono RCA cable is two wires, and it goes to the turntable where it's still two wires all the way up to the cartridge, and inside that the two wires are wound into a tight little coil where they connect in the center. Both channels are like that. They're nothing more than a big loop coming off the phono preamp - that's wound up tight at one end. So the only thing you can do is try to use one side of the loop as a shield by wrapping it around everything, and not using anything on it for signal.