Hi there, @ldelorme ...
I just had a similar conversation today with one of our instructors...about assignments and peer reviews...specifically about the "Assign Reviews" date box. The instructor was wondering how that date is used. If, for example, Student A submits the assignment after the selected "Assign Reviews" date, then the two students (Students B and C) weren't automatically assigned to peer review the assignment submitted by Student A. However, if Student A did submit the assignment before the "Assign Reviews" date, then Students B and C were automatically assigned to Student A's assignment for peer review.
Initially, I wasn't looking at the right Guide that confirmed our suspicion, but then Canvas Support pointed me to the correct Guide:
How do I automatically assign peer reviews for an ... - Instructure Community - 899
Now...related to your question... It does appear that you've found a slight difference between the screenshot under Automatically Assign Peer Reviews and the text description underneath it. I'm not sure if you are aware or not, but if you take a look at the Guide you linked to, near the very bottom of that page, you'll see a blue "Leave Feedback" button. Clicking on this button brings up a short form to fill out where you can submit any errors or suggestions you see for this specific Guide. The Canvas Documentation team will then review your feedback and make any necessary changes to the Guide. The change might not happen immediately, but do know that they will see your submission and evaluate if anything should be changed.
I hope this helps in some way!