Solid Union leaving too many breps

I am using Solid union to connect 21 small pins to two geometries. The result I want is for the union to connect the pins and the larger geometries together so that there are only two Breps left. However I get 6 left. I tried flattening both data trees but that did not seem to work. Any ideas? (7.5 KB) SolidUnionProblem.3dm (12.2 MB)