Hey, I’m sure Joe or Bryce will come with a more in depth reply to this. But i can tell you what i’ve been doing running these programs.
So i think their intent with the first phase is so that you get to know the exercise and pin down form before you start going to failure. If i’m running one of these programs and i feel confident in my form on the different exercises and my recovery is on point i will «speed up» the program. So as an example i take 1 week in phase one going 2-3 reps from failure, 1 week in phase two going 1-2 reps from failure and then move along to phase 3 taking the sets to failure. From there just grind it out and milk it as long as you are tracking progress on the lifts.