i used to do weight watchers (lost a ton of weight, but wasn't healthy), and i was sort of primal in that i didn't eat a ton of grains...mostly chicken and vegetables. but i was always hungry and lost of a ton of muscle mass, and that created some problems. weight watchers and primal are trying to achieve the same thing, but from different angles. WW pushes low fat and high fiber. PB involves a decent amount of fat to keep energy up because it's low carb (whole wheat bread is an evil murdering murderer). one primal meal might kill your WW points allotment for the day. adversely, WW gives zero points to fruit, which can derail your primal success.
that said, there's no reason you can't practice some portion control with primal foods. if you need that structure, just focus on calories or grams of macronutrients. create your own points system if you want, but i recommend against using WW's point system.