Not being a structural engineer nor an expert in zebrawood strength, I don't feel qualified to be able answer your question accurately or with any degree of authority.
However, as an old broken down bowhunter and long time Bear collector, it seems with Bear's vintage I-beam riser (three vertically laminated slabs), isn't the center slab the most nearly completely intact (not to mention the slab with the most glue surface area), and logically wouldn't it be desirable for the center slab to be the strongest of the three pieces of wood?
Wouldn't the two outside slabs likely be the least intact (weakest), and could be made of more decorative pieces of wood rather than the strongest pieces of wood?
That interesting slab of wood does have a hole drilled for the Bear coin, outside dramatically rounded contour for the grip, and just one of the long sides glued for strength.
Sorry to answer your question with more questions. Hopefully if logical questions are asked, some answers become apparent.