I agree that the majority of the surface of an Infusion's hull is symmetrical. However, the beam landings are not symmetrical about the same plane. The rules could say that the beam landings don't need to be symmetrical. But, the rules need to define clearly what a beam landing is.

Your hexagon example isn't a problem. The hulls could be cylindrical and they would still have a plane of symmetry. A hexagon has 6planes of symmetry, a cylinder has an infinite number of plane sof symmetry. They key is that the rudders and daggerboards are on one of the planes of symmetry.