They did, because other people figured out something was up and the speculation was considered more problematic than holding out a few days.
As you say, the vulnerability was disclosed to others on the 1st of June, which puts us at 6 months for the disclosure deadline. If 6 months in vendors aren't ready with patches I doubt those few days would have made a significant difference.
As you say, the vulnerability was disclosed to others on the 1st of June, which puts us at 6 months for the disclosure deadline. If 6 months in vendors aren't ready with patches I doubt those few days would have made a significant difference.