This is not how things work. In a crisis like this there is a war room with all stakeholders present. Doesn’t matter if it’s Sunday or 3am or Christmas.
And for this company specifically, Guillermo is not one to defer to comms or legal.
They can be brought in to do their job on a Sunday for an event of this relevance. They can always take next Friday off or something.
If the attacker is moving with "surprising velocity," every hour of delay on an email blast is another hour the attacker has to use those potentially stolen secrets against downstream infrastructure. Using Twitter/X as a primary disclosure channel for a "sophisticated" breach is amateur hour. If legal is the bottleneck for a mass email during an active compromise, then your incident response plan is fundamentally broken.