"Dismember" I use for living creatures, the act of removing their limbs/body parts (cf. L. membrum), but for mechanical/non-living things, I would use dismantle or disassemble. I suppose that in the case of hunting animals (or monsters, in this case) I would feel far more comfortable with "butcher", e.g., "They butchered the deer," since the intent is not only to remove the various parts of the animals, and not simply a particular part thereof (cf. "skinning", "scalping"), though "to butcher" (along with "to slaughter") in general usage also connotes food processing.
At any rate, I leave it to the wisdom of the translator/proofreader; there might be nuances that I am not exactly aware of. My personal guess is that they used "dismantle" because "butcher"/"slaughter" may have connotations of brutality or violence for some readers, though as someone who has helped butcher chickens and pigs (and a few other animals I will not mention, lest the wrong sort of crowd squawks at me), I do not believe that I will ever say that I "dismantled" those animals. Each translator/proofreader to his own, I guess.