I thought that change requests begin at execution as they appear as outputs only from Executing and Monitoring and Controlling Process Groups.

However, I just reread on page 122 of PMBOK that "If approved change requests result from the Create WBS process, then the requirements documentation may need to be updated to include approved changes." Also, on page 93, it notes that ICC is conducted from project inception through completion. 

So, does this mean that for all planning processes that list outputs as Project Document Updates (which can include the project schedule), that Change Requests are needed to modify them? I thought that during planning those updates would just be a form of progressive elaboration.

Thoughts?