Yes, it has been confirmed by the devs, I had the same question in bug report because I had a duplicate card but one of them was increasing in their overall positional rating.
The response was that yes, development does not occur but gaining experience/games played at positions does exist. So while a player will not change their arm/range/etc, they can gain experience at different positions.
http://www.ootpdevelopments.com/boar...35&postcount=3