Some of the items give the wrong amount of boost power for their weapon category.
For example, a common yellow sword has gives 480 boost to Annihilation (in both categories) but IIRC, the common heat sword gives 400 (in neither category). Some common and rare shotguns seem to be wrong too.
I'm not sure if there is meant to be two categories of side weapons, or if it's just a bug. Flamethrowers and mini guns and some others seem to be in their own category and don't usually boost regular side weapons properly. Either way, there are bugs with some of these items.