Well, not exactly....
I am a DC member, and I always call the 800 number, even though i didn't book my reservation through the DC. They have never asked me for my membership number unless I specify I want a DC rate.
The 800 number links you to the WDTC. Some people don't like dealing with WDTC, for me I have not noticed a difference. If you call the 800 number and say you want to book a room only or you want to use a code, they will transfer you to CRO if that specific CM is not capable of making a CRO reservation. As far as I know, any non-package ressie is done through the CRO system regardless of what number you call.
So, I always call the 800 number. The waits are always shorter, and its free. It's 800-828-0228