I didn't notice these till yesterday... The button is spring loaded. I'm not sure how wobbly the tire would be as it seems to let the spinner back off about 1/16" from the hub, but it would stop it from flying off.
Talked to Joe today and he said they've had these for about a year and a half now. The anal side of me wants to put the safety wire on as well.
I also finally posted the delivery pics in my gallery...