Neal,
I think you are missing the point that the others are discussing.
It doesn't matter if the "ship" is in a narrow channel or a TSS, the
Rules are still holding them to the stand on/give way status under the
Steering and Sailing Rules.
However, because the vessel which must stay in the narrow channel or
TSS, is working under conditions which potentially limit it's ability to
comply with those rules, they have stated that the vessel which is not
restricted to those confines, shall not impede, even though it may be
the stand on vessel.
They have not relieved the ship of it's obligations, they have just put
the greater obligation onto the smaller vessel to understand those
conditions and give way, no matter what (stand on or give way).

otn