Well, I find that rule of thumb works more on the ladies than the guys. Have you seen the non-dancing shoes that women wear when they go out? A lot of them have very thin high heels with nothing to strap their feet in, some of them have thongs or platform shoes with no straps. I think that experience dancers are capable of dancing in those, but I'll bet they would rather be in dance shoes. Whereas, I've seen guys in regular dress shoes but they all hold onto their feet. It may be harder to spin on rubber soles than swede or leather, but it still can be done.