Do you have a source? Google got me only KRACK, which doesn't mesh with your comment. They did participate in that embargo, for six weeks, then refused to extend it to three months because the information was widespread at that point, including to US government agencies, so they felt it likely to be exploited. They communicated this beforehand, got the OK, then patched it silently, which while potentially revealing is no announcement. Their actions seem consistent with a goal of minimizing exploitation across the industry, not some quixotic dedication to non-secrecy. Even the least charitable interpretation of their behavior would lead one to notify them weeks beforehand, not hours.