The most relevant information I see on this is Google's comment that future claims about past events will not be subject to binding arbitration. That implies th

The most relevant information I see on this is Google's comment that future claims about past events will not be subject to binding arbitration. That implies that the special circumstance which will be different going forwards is not about underlying events, but about the actual current status of the claims. If the announcement set Day 0 based on the date of the claimed harassment, that would be extremely suspicious, and I think the most natural reading would be some specific issue that's been resolved, but could produce exceptional damages. With a date-of-claim threshold, that seems much less likely; any kind of serial misbehavior or other mishandling that Google expects to avoid in the future could still create liability via claims not yet filed. A few legally-inclined people elsewhere in the comments have pointed out that "adding the option to leave arbitration" behaves differently than "not forcing arbitration to begin with". Most non-forced arbitration is still binding, which means that neither party can start arbitration and then pursue a lawsuit after seeing the result. Opening a one-time option to leave ongoing arbitration would be much more similar to entering non-binding arbitration, a move lawyers frequently counsel against. The proceedings of non-binding arbitration are almost never admissible in subsequent court cases, and the process lacks formal discovery. As a result, there are unpleasant tactics like entering non-binding arbitration, obtaining useful information (e.g. someone's schedule, or information of who knew about a behavior), and then pursuing a lawsuit with added or altered claims based on that information.