They are meant for bull riding and usually have locked rowel.
You don't want a locked rowel for riding a horse. You are not using the spur to gain traction,lol, you want to be able to roll the rowel up their side. You can't do that with a locked rowel bull riding spur.
If the rowels spin, I woulnt worry a whole lot other than you are going to get a few looks :) But I do believe in picking a spur to help you achieve the best response for your leg length, horse size and ability. Depending on those factors you may want to rethink your choice.
I DON'T LEAD 'EM AND FEED 'EM, I RIDE 'EM AND SLIDE 'EM.