I'm sorry but I just have to point out that an arm makes no sense. There should be at least also a frame for the torso and some artificial legs. Otherwise all that arm might give you is enormous strength in your handshakes or some such.
Then again maybe the feature of the artificial arm is exceptional precision of movement or something like that ?!?
My previous attempted reply got mutilated (and only showed the quote), so sorry, trying again:
You’re absolutely right there, and that specific issue was explored in the Ghost in the Shell manga, as a reason (IIRC, fuzzy memory) that people would opt for full body prosthesis rather than just having a super-strong replacement arm, complete with cute cartoon (different art style) of an arm trying to pick up something heavy and ripping itself out in the process.
Aside from the possibility you brought up, for symbiosis experiments, an arm does make more sense than other appendages. At least if it decides to stop listening to the host, there’s no mobility impairment, so the poor host can run around for help screaming whilst the arm is punching them in the face rather than trying to ambulate in some manner with an uncooperative leg.