optionality of 'pdpURI' attribute in AssemblyTemplate is inconsistent

WD13 specifies the 'pdpURI' attribute of the AssemblyTemplate resource (section 5.8.3) as "Required: false". However, the two mechanisms for creating an AssemblyTemplate described in 6.12 both say: "The server shall include the pdpUri attribute, which identifies the PDP from which the template was created, in the newly created AssemblyTemplate resource." It is inconsistent to describe an attribute as being optional yet require (using normative statements) every implementation to include it.