I have now come to realize that Peterson has simply not spent enough time in Foucault literature to make a very good assessment of his work, ex: he thinks Foucault was some identity politics monger, this is debatable to say the least.
It's also a mistake to say that Foucault was a pure social constructionist like some of his acolytes that hack away at his work, or he misunderstands his critique of subjectivity.