The article and rules make clear that this applies to the companies writing and submitting fraudulent reviews, not the platforms hosting them.
(If Amazon wrote a bunch of its own fake 5-star reviews for products under its own label, then this would apply in that case. But considering how many Amazon-brand products have terrible ratings, there's no reason to believe they've ever engaged in that practice.)
I didn't see any of them grabbing the password, but they easily could have.
I'm pretty sure Apple has since closed this loophole by enforcing that apps perform OAuth in a browser where they can't control the DOM, but I'm not sure - I got as far away from that scene as I could...
Apple are not restricting OAuth in an embedded web view, at least not on a software level. I have worked on an application that injected JS into the OAuth window for non malicious style purposes. It is possible they're rejecting apps from the store for this behavior, but I wouldn't know.