That is, indeed, what 9-9-6 means: 9am-9pm (12hrs) * 6 days per week.

9-9-6 is also not full productivity for 9-9-6.

Office workers will eat lunch, take a 1-2hr nap in the afternoon, and also eat dinner with their coworkers within the common 9-9-6 rhythm. It still takes a significant chunk of time, but the actual working time butt-in-chair is closer to 54 hours

You lose productivity doing 996 anyways so how can you maximize past that?