IMO, the reference to "professional class" meant the class attracts people who make a living doing sailing related things to its events. Usually because of the chance at exposure.

Example: Tornado Class at the Olympics. Think someone trying to make a living making sails/building hulls/driving boats wants his product to win the Gold medal? Yes, b/c the exposure can lead them to bigger and better things. This does not imply that professional Tornado sailors, shun other classes - they are attracted to racing the T for the chance at exposure, as they would be attracted to F18, A Class, monos too, etc.

I do not think there is a class for professional sailors only - except the V40's maybe.