The reality of joins in plywood panels is some strength compromise in the plywood joint of a panel is offset with the much stronger glass epoxy glass layers covering the joints. Puzzle joints and finger joints also glue area to the joints but both are machined joints more suited to kits. I do not trust step joints or spline joints and puzzle joints and finger joints are not worth the effort in the home shop. Because I build without kits I will stay with the strength and consistent flexure achieved with scarf joints.