It becomes important later when you've finished the main part of the afghan and are ready to add the border. The pattern is making sure you understand which side it's calling the right side because that's the side from which you'll be picking up stitches.
It may also help to mark the right side (RS) of the afghan so that you'll be sure to knit the rows on the right side and purl the rows on the wrong side (WS). A safety pin or a loop of yarn will work.
Very nice project. We'd love to see a photo of the finished afghan if you'd like to post one.