The first style of one piece handle I made included a notch, which required the maker to laboriously fit that notch with the top end of the first shaft strip. It worked, and still does, but it was a time consuming step in the project.
The new handles remove that back side notch. This means that the top of the first shaft strip can be left square, if desired. Or you can shape that top end as you see fit and leave it. Or you can cut side pieces from scrap and epoxy those side pieces in place. Once dry the handle backside can then be shaped to the maker’s desire.
I like adding side pieces, most of the time in a contrasting color from the shaft piece and/or the handle itself. It’s another option for customizing your paddle. Best of all, I think it improves the process of mating the handle with the shaft.