He answered a question about collapse, not Born rule, it's two different phenomena. Decoherence replaces collapse and explains why you observe one result, Born

He answered a question about collapse, not Born rule, it's two different phenomena. Decoherence replaces collapse and explains why you observe one result, Born rule is replaced by the law of big numbers. Born rule is an abductive explanation for empirically observed statistics, and as abduction allows alternative explanations, it's empirical observation that needs to be explained, not postulates. Ironically, the law of big numbers is calculated MWI style: it considers all outcomes equally as if they all happen somehow even though they are mutually exclusive, but they all add up to the final statistics of statistics. The Schrodinger equation gives your state, you project it to the Born rule basis and see the projection asymptotically approaches 1. What's left after that is how to interpret asymptotic certainty, but that looks easy.