A hook slot ( especially ), or any other mold bulge ( belly ) or choke point will impact how the plastic flows into the mold. This will inherently create a vortex spot. ( Like smoke in the wind tunnel going over a car top or plane wing ). Add to that the differing viscosity of transparent versus pearl colors.
Some molds, due to their design, will not lend themselves to a really clean twin-jector laminate. If you look at the DD gill mold; it is almost a perfect mirror image mold between the halves; and that is reflected in the really clean laminates that several have posted pictures of. But; I don't think many fish care nearly as much about clean laminate lines as I do.