Here's how I break it down:
Graphic Design is for How it Looks (bodywork and finish)
User Experience is for How it Works (cockpit and control layout)
Code Review is for What Makes it Work (engine, frame and moving parts)
There's certainly some overlap -- UX might spill over into either of the others -- but that's the rough division.
What an object should ...
I think it is on-topic for either here or UX.... And my personal opinion is, if it follows the critique guidelines, (What are the guidelines for asking for a critique of my work?) I wouldn't see an issue here myself.