As the technical lead for code review, I'm glad you're trying the feature!

Anyone can set the target stream of the code review. We prefer that the author does it because that shows where the author wants to deliver the change sets. There aren't any limitations on who can set that field because we don't want to block the review if the author sets the field and goes off on vacation (for example).

If the feature gets enough traction, we'd love to include an autodeliver feature as part of code review. In that scenario, when a sufficient number of approvals have been given, the change sets would be delivered to the target stream.

Under the covers we use the target stream to resolve the paths within the change set. It is possible to find those paths in other locations, but an explicit delivery target is most accurate.

For more information about RTC Code Review, see:
Article: Rational Team Concert Code Review
Video: Introduction to Code Review (Part 1)
Video: Configuring Code Review (Part 2)
Video: Performing a Code Review (Part 3)
Knowledge Center: Working With the Code Review Tool