Arbor started doing it a few years ago. A couple models of Stepchild boards have it now, as do a couple DC models. It's called a Structurn base. Arbors that friends and I owned with that base were all pretty fast. Not sure how much of the speed was from the sintered material used or this tech, but it definitely wasn't any kind of drawback.
15 NS Ripsaw . 14 NS Proto HD . 14 NS Cobra . 13 Gnu Space Case EC2 . 2013 Salomon Pow Snake
14 Now Drive . 13 Now IPO
14 Flow Hylite