I just remembered the fast packs on the VF-11B also have a fairly visible sprue mark on the left side.
(original image at http://gamu-toys.info/goukin/yamato/vf11b/02.html )
I am sure they are cut at the factory, not just ripped off the tree since it would look even worst. The cannon also has a round surface and make it harder to cut cleanly. If you have built some gundam models unpainted you would also notice that it is impossible to make clean cut on large pieces since the sprue point will be larger to allow better injection of melted plastic into the mold.
I would agree that at the price level they charge they could have done a better job with the mold to hide the sprue mark at hidden surface. But we are not going to get pro-modeler level of careful cutting, sanding and painting at that price. And with extra treatment they are still toys with screw holes all over them.
Even the weathered version have this problem. Just look at the calves part on the 3rd pic:
http://www.hlj.com/product/YMT00122