I have always thought that expat refers to those who maintain their citizenship of country of origin (an American citizen living in Spain) and an immigrant is someone who is either a citizen of the destination country or on the path to become one.
I, too, am interested in reading the critiques. He seems to pepper much of his podcasts with YMMVs and ”case by case” knowing full well that there is no “one size fits all” or panaceas.