I have to agree here. I have built two Model IVs and just checked the manual. The butt rib is installed with the capstrip extension inboard. The only issue that may come up from that is if you use screws to install the windshield/skylight. It will made a bit more challeging tightening the nuts. I used nutplates for this reason.
I suspect the instructions to put the capstrip extension outboard is a misprint that somehow crept into the new manual. Or possibly an alteration of the original instructions to facilitate the subsequent installation of the windshield without then modifying the dimensions of the mounting parts.