They may not look as sturdy, but the "fingers" do appear to be hub-centric, and pilot the wheel. The slots aren't an issue, since it's the wheel bolt clamping load, and the resulting friction between parts, that prevents "slipping" on the hub, not the acutal bolt holes. If it were truly a shear fastener application, you would never use wheel bolts, but studs with no threads in the joint interface.
A quick Google as an example:
http://www.maximummotorsports.com/store/index.php?main_page=tech_wheels_spacers
Threaded Mode
