For reflow soldering they really don't have to be that precise. Capillary action pulls the part into place and aligns it as long as it's somewhat close when the

For reflow soldering they really don't have to be that precise. Capillary action pulls the part into place and aligns it as long as it's somewhat close when the solder wets, it's really neat. Even QFN packages the author mentions don't really need to be that precise, for those it's more important to get the right amount of solder paste dispensed so that you don't have bridging of pads.