Here is my updated understanding. Again, feel free to correct me if I am wrong.
According to this FAQ
http://www.edd.ca.gov/jobs_and_training/FAQs_WARN.htm
There is a defination of "layoff date": "A worker’s last day of employment is considered the date of that worker’s layoff."
So the Oct. 11th we are talking about is NOT the "layoff date". It is the notice date. On that day, if there is a layoff, impacted empolyees and both state and local representatives will be noticed. Then impacted employees get to be on payroll for other two months, which fulfills the 60 days requirement of WARN act. Then after that two months, Dec. 11th is the layoff date.
So even if there will a massive layoff notice on Oct. 11th, it is normal that it does not show up on WARN report before Oct. 11th. As a reference, notice date of the layoff on March 1st is March 1st in below report.
http://www.edd.ca.gov/jobs_and_training/warn/WARN-Report-for-7-1-2016-to-06-30-2017.pdf
Posted by @Pz70LSP-1dyl, bumped for info.