Are you trying to go through the purls from the back, left-to-right? Or a different way? I don't see how having the other stitches closer to the tips could get in your way.
Yes, you could increase by doing a yo or anything easy, but she obviously has written it to preserve the look of the cables (and you must have liked it or you wouldn't have bought the pattern). If you can't find any reference to it online, I suggest you e-mail Cookie and ask clearly about anything you're finding difficult. Every time I've felt I had to e-mail a designer (okay, twice), they've been very helpful.
(Include a quick compliment on her beautiful designs to butter her up. Also, it's Cookie, her patterns rock, and she deserves it.)