I assume it's related directly to "It’s been quite some time since our last update but, after consultation with law enforcement, we’re now in a position to give more detail".
Discovery, immediate mitigation, deeper mitigation, general notice, notifying effected users - all these can happen pretty quickly once the ball is rolling. Once you're dealing with "the law" in any capacity you are constrained in what you details you can share broadly, and when.
I'm happy we were finally able to share this level of detail.