I'll have to double check next time I'm at work, but that doesn't make much sense to me. If there is something causing attendance issues, you might need some time to get it fixed or get into better routines or something.Critical period is where you can't screw up at all. You've already been coached a bunch and that was your chance to get your self together. I.e, if you are in critical period for attendance, you need to be at work as scheduled every shift. For the rest of the CA, you need to show that you can maintain improved attendance--not have perfect attendance.
It's easier to use a performance issue to explain this. If someone is just terrible at the job and has been coached, you can't expect them to be amazing at it on the first day after you deliver a CCA. They need a month to improve and get better at the job. If they still aren't performing after you gave them a month to improve, then they might need to go to a final (or more coachings and then a final). If they did improve in that month, then they need to maintain that level of performance for 6 months.