I mean, I assumed he built his robotic arms and has to have the know-how of an engineer in order to maintain such a mechanism.
I actually think engineer fits, he seems like a being who would help design and maintain complex machines, and from the look of this moc, war machines at that. He reminds me of a techmarine from Warhammer 40k. I don't think the name warrants a four point deduction. If the build is good, and the name doesn't truly represent the moc, I'd give it a 9 at least, since I still think the moc is really good, even if the concept wasn't properly represented.
I'm saying this because the builder hasn't really given much in terms of the story behind the moc, which is understandable if the moc can convey a story by its build alone, and my interpretation is that this "engineer" is a person who maintains war machines, maybe his own, and has built his own robotic arms in order to carry out his tasks. I'm assuming the title was self-proclaimed and maybe the being itself is part-machine or even an android, justifying the need for knowledge of designing, building, and maintaining machinery.
In short, I don't think misnaming a moc warrants such a low score, especially if the build is impressive. Be that as it may, a name can always be changed as well, if the creator is given a valid reason.