My build manual said that too.
However, the Polyfiber manual says you must mechanically attach because the force that will remove the fabric from the rib is a peeling force and the width of the rib is irrelevant.
I agree that the riblacing became enjoyable once I got the hang of it and it really did not take that long.
I saw one Kitfox years ago that did not appear to have any lacing but I know nothing about the owner or how it held up.