Charles,
I kind of agree with you in one way: If you are sailing on protected waters, meaning relatively flat water, you can safely sail and control cats in much higher winds than if you are also dealing with big chop. Same thing if you are out on the ocean and have no current or boat traffic causing chop and all you have to deal with is long, smooth swells.

Sometimes you can find ideal speed conditions on an inland lake in Kansas.

So the "safe limit" for racing or pleasure sailing actually has a lot to do with the water conditions as well as the wind conditions.