There are a lot of people in the fitness community who think that if some exercise is good, more must be better. I'm here to tell you that mentality is just not the right one to have. If you're training your body to grow muscle, build strength, and increase work capacity all at once, you're going to need rest. Change happens during rest, not during work.
In Phase 3, you have four rest days per week; two are during the week, to break up your workouts, and the other two are designed to give you two consecutive days off. These can be "active rest" days of low-impact cardio, swimming, walking, hiking, or yoga. If you must go to the gym, I suggest a "bro" day of arms and abs.
You may be used to doing one or two workouts per day, but I don't think doing that sort of volume is the correct way to bring results, especially if you want to build and maintain those results in the long term.
These workouts should be intense and difficult. If you can get through them without breaking a sweat or breathing hard, you're not doing your job. Work hard when you train, and allow your muscles to do their job when they're resting.