It sounds like the person is using the behavior to feel more "supported" acting out one's fantasy world a bit? I don't think it hurts anything but it might become habitual and cause social problems or allow the person to only interact with themselves in their fantasy which, over time, can be a habit that is hard to break? I would talk about it with the person, see what is going on and if they have thought through what they are doing.

If it is taken out in public (or too far in the person's mind) it can turn into malingering, the faking of a disability. I remember seeing a spot on TV quite awhile ago where a professional (I think she was a lawyer) started using a wheelchair when there was nothing wrong with her legs and how hard that was for her to stop/admit to clients she had not needed a wheelchair for the last 10-20 years, whatever it was. The whole dual thing stressed her so much she had to give it up but it was really really hard to walk in to a group that had never seen you other than in a wheelchair and admit the bad habit/fake?