The neutral and ground are not allowed to be connected together (with
few exceptions) other than at the service. The neutral connection to the
ground bar at the disconnect is a code violation.

I agree it is a code violation, but why?
Normally it is prevent grounds from being energized unnecessariy; when they
are connected to the neutral there is a potential to get a shock off the
ground.
But in this case the wires (or so I presume) go directly from the disconnect
to the breaker box. There is no chance for anything unfortunate to happen;
so why is it a code violation (except that it is...)