I wondered that myself...best I can figure is that they push on the outer race of the bearing...but still strange because...the bearings don't have an outer groove for them to lock into...almost like a half ass adaptation to what you would find in industrial equipment when a set screw is in fact used to secure a bearing for assembly ...or to prevent the outer race from spinning in loose fit housings. ...
some industrial applications use anti rotation pins..etc..
but in this case...whenever I looked at it...i wasn't sure if they even lined up properly on the hubs...