I never said the boat wasn't well built. I am saying that the training and response of the crew helped save many lives. Even without a hole in the pressure hull, USS San Francisco could have easily sunk if the crew hadn't responded as they did.
When I reported onboard my first boat, USS T. Roosevelt, there were still people onboard that remembered when it bounced off an uncharted mountain. Like the 711, the 600 was in transit, and was at depth and speed. Unlike the 711, they did have flooding, but the force of the impact tended to bounce them toward the surface. The torpedo room was isolated, with personnel inside, and was pressurized to help keep out the ocean. The hull was repaired, and the boat served many more years, although it had a shallower test depth than the rest of its class.