Just my opinion, its all a numbers game, based on how many the company needs to get rid of, how many are there. I received a 1 based on sales numbers, but was not pip'ed (I thought at the time my manager was supportive and thought it was bs - I mean all 5 of us sold the same product mix, all 5 had the same numbers essentially). I did get let go, last December. They retained a rep with less than one year with the company, aka, she had no sales numbers from the previous year. They go over the criteria during the layoff call and it is based on sales numbers, geography, tenure. I think there will always be examples of people who don't fit the criteria (where some were let go who had more tenure and better numbers than others).
From what it sounds like, this layoff (again, just my opinion) will be so deep that its going to affect many reps, probably some that never had a 1, etc. So best not to try and guess, worry and stress....just have your resume ready and start networking now. It is a very different world looking for employment now than it was when I started in pharma over a decade ago....