The Milgram experiment is the other member of the "top two" that I refer to in the post.

I could be mistaken about the ethical approval being brought forward, but that is what I recall being taught while an undergrad at Stanford. The Milgram experiment occurred years before the SEP, and I seem to recall that the fact Zimbardo was able to get approval for this experiment (including getting the local police to help) led to a huge crackdown at universities.