For the above topic, I think it really depends on the type of PT you are doing. The body needs time to repair/adjust and after one muscle gains power, it takes time for the rest of the body to learn to properly use this strength with other groups to add, isolate and release energy. As an injury is repaired, different body parts change and with the restoration of connection to the injury, these muscles that weren't severely injured will require adjustment and periods of rest as well.
That's not to say there isn't almost something that can be worked on but rest is often better than vigorous exercise for the body, especially if it's one body part/area that is continually carrying the load.