No question the so called motion hole impacts static weight. That is why we always called them balance holes, even when we weren't using them for balance, but to create a different roll. My first experience with holes was using axis holes on a pancake block Black U Dot, and Black Angle. It definitely smoothed out the break point, although those balls already had a smooth look by todays standards.
I have also used extra holes on two piece balls, both symmetrical and asymmetrical. The impact of those holes seems to vary considerably depending on the core structure of the ball. Little impact on asymmetricals. Noticeable impact on some symmetrical layouts, but less so on others. Extra holes clearly impact static weight, but can impact dynamic balance of some balls also.