What groove t says is right. With straight line tracking air bearings you wind up with 2 small resonant bumps rather than one big one that occurs in regular arms
The horizontal mass is considerably higher and somewhat an advantage when you consider what the stylus is forced to do. The needle is carrying and responsible for movement in 2 planes instead of 1 fixed pivot point of regular arms and hence the 2 resonant points occur
The Dynavector 505/7 tried the same thing, with high horizontal mass and another shorter arm with similiar effects due to 2 different pivot points
They also used an internal spring bob and spring to cancel out resonance that worked well but the arm suffered from warp wow because of the short pivot arm transversing warps
The splitting of the pivot points gives you different motional impedences in comparison to one fixed mass over the stylus. You have a moveable weight carried and moved horizontal differently by the stylus compared to vertical.
You wind up with 2 effective masses instead of one
The goldmund would be still be a single fixed pivot point seen by the stylus since a sled is pulled and you still get one resonant point
I sure someone can explain it better