The CSD Unit is normally integral
with the generator; therefore, the disconnect is between the CSD and the engine
gearbox; not between the CSD and the Generator. Therefore, it's only the CSD
that can be disconnected from the engine gearbox.
The disconnect is there for the
purpose of isolating a hydromechanical unit i.e. it might either be leaking
oil, overheating, or causing the load sharing system to do oddball things. If
you operate the disconnect, it will dump the generator via the CSD i.e. the
rotational input from the engine gearbox is removed and resolves the oil
leak/problem.