The reason I'd cut out the rectangles in the vise support was that I'd intended to put a benchdog hole through each, and I wanted the thickness of the top to be the same for all of the benchdog holes. Where I messed up was in not cutting out the ends, between the bolt tabs. I'd intended to put a benchdog hole through there, as well, but I'd forgotten to cut out the segments prior to glue0up.
Grizzly is a company currently undergoing an upheaval. This brand was once known as a manufacturer of professional grade tools and equipment for woodworking products. Though, in recent years, that reputation has begun to slip a bit since being bought by the Chinese company SIEG. These days, whether the Grizzly product stands up to its previous standards of excellence often has more to do with what you are buying than the company itself.