Given that the holidays occurred during the 90-day period, and that Microsoft was paying attention and made a fix, and that testing found an issue with the fix,

Given that the holidays occurred during the 90-day period, and that Microsoft was paying attention and made a fix, and that testing found an issue with the fix, I think it would be reasonable for Google to give Microsoft an extension on the deadline. The statement that "if 90 days elapse without a broadly available patch, then the bug report will automatically become visible to the public" is little more than Google claiming the computer made them do it.