DNK
250.50 directs us to bond TOGETHER all of the electrodes that are present(05).
250.52(A) Electrodes Permitted for Grounding
This is where I think your confusion lies.
.52 shows us the electrodes that are permitted to be used for electrode, .50 tells us the ones that are present are required to be bonded together to form the grounding electrode system, cold water being one of them.
If the cold water is used for the electrode, it is required to be supplemented. The reason for this is not because it is not a good electrode (on the contrary), but because so many repairs today eliminate the copper pipe with plastic, and the plumbers making these repairs are not worried about our grounding electrode systems.
