Okay, sure, but at what point does it really make sense to carry that around vs an equivalent (or much less) in frag mines? Granted I haven't gone through all the content but I can only think of maybe 2 or 3 situations where boosted trap damage would justify hauling that weight around, and even then opting for that over just using a frag mine and having room to carry more regularly useful items is a hard sell.
The skill's logic is backwards; rather than how it is now, Shift+Action should be used in the less common situations where using an EXT item would make a difference (hardly ever from my experience). The standard Action should just call rocks and be done with it, since IMO 95% of the time standard Rock trap damage (effectively doesn't have a weight profile) is acceptable because either killing the enemy is not time-critical, or you just need to soften the target a little bit to get them into OHKO range.