I'm a little surprised that they didn't try to re-engineer this to make it work after making such a big deal about it earlier. Seemed like a neat design for a mech. If it wasn't going to work long term though, I suppose it makes sense to cut it, and it's not unprecedented to make mechanical changes from test games to production. First examples that come to mind are the Deadworld mech on JD, and the big 3rd gopher on NGG (that was supposed to be under the disc).
Having not played POTC yet, I can't say how the motion of the disc rings changed the ball path, but this will probably change the way the game shoots/reacts.