The 60 days of employment is a requirement of the WARN act (https://en.wikipedia.org/wiki/Worker_Adjustment_and_Retraining_Notification_Act_of_1988)

When employees are laid off at Google, they lose access to any systems, can't contact co-workers in the usual manner, etc.

Google severance has been increasing worse since they had their first 12,000 employees get laid off.