I have heard that some states (like Florida) make a distinction between a fifth wheel and a ball hitch (gooseneck) which is why you see the vast majority of toterhome rigs using a gooseneck instead of a fifth wheel even though they are a pain in the ass and have a lower weight rating than a fifth wheel. I guess for all legal purposes a ball hitch is a ball hitch, regardless of the placement on the bed vs. the bumper.
And yes, the wording of that Florida statute above is ludicrous in the real world, ANY trailer has to carry some of the weight on the hitch. I'm sure the intent of the wording is a true semi trailer where the load is evenly distributed between the trailer axles and the tractor axles. But I am also sure the dumbass bureaucrat that wrote it never towed a trailer in his life.