I agree with Eric, you may not get a satisfactory answer on this, but on page 70: "Figure 4-1 provides an overview of the Project Integration Management processes. The Project Integration Management processes are presented as discrete processes with defined interfaces while, in practice, they overlap and interact in ways that cannot be completely detailed in the PMBOK® Guide."
Looking on page 596 are closely linked and that process does create change requests. So perhaps the change request is not emanating from the manage project knowledge process, but rather the output is a new project document we need to manage (a new version).
Interesting catch - because most of the other executing processes do produce change requests!