I think what Uber means is that the computer mouse is generally placed on the right side of the keyboard-- so it's a learned habit that the mouse should be on that side.
My mother, aunt, and grandma all move the mouse to the left side. Though, they're the only lefties I have seen do it.
Would it make sense if I said I also notice that people generally wear watches on the opposite wrist of their dominant hand? [This could..er..be neutralized by those who are ambidextrous, of course]. Though every time I've seen a watch on the right-hand wrist, my guess at that person being left-handed has been correct... so...just wondering..