This is common misinformation. Even in this case, OpenBSD did not break the embargo. After protesting, they received the permission of the researcher to publish:

  Note that I wrote and included a suggested diff for OpenBSD already, and that
  at the time the tentative disclosure deadline was around the end of August. As
  a compromise, I allowed them to silently patch the vulnerability.

(https://www.krackattacks.com/#openbsd)