There is certainly merit in calling the landing roll-out of a CAT III approach part of the approach. Having said that CAT III approaches are unique in their requirements for aided roll-out guidance.
Once down to taxi speed, though, the approach is over. Granted, getting to the gate can be very difficult;nonetheless that is not part of the approach procedure.
Although not advised, the airplane could stop on the runway and sit there for a very long time, or a few hundred feet off the runway on the taxiway. So, when would that be considered parked?