Does anyone know of a rule that states you cannot include harvested Rainwater in your WEc4 calculations?

As part of our submittal for an Innovation Point for Process Water Use Reduction in an Industrial Facility (a facility which uses far more process water than a school ever could) patterned after the credit for Schools, we added the fact that Rainwater will be harvested and used which accounts for approximately 12% of the more than 25 million gallons that will be saved annually. Part of the GBCI reviewers response was:

"Note that the rainwater collection strategy would not be applicable to an ID pursuit for Process Water Reduction; therefore the water savings reported for the rainwater collection system has not been taken into account for the purposes of this credit review."

I have searched through every LEED Reference Guide, Addenda, CIR's, and LEEDuser. I cannot find anything that confirms (or denies) the reviewer's comment. Can anyone point me to where they got this?

Thanks - Kris