Disclaimer: I’m trying to give some potentially helpful info but, at the end of the day, I’m not a lawyer, nor an expert on the WARN Act.
It doesn’t appear that any of the Optum layoffs were reported and on the WARN report, at least not for California. (Reference: https://edd.ca.gov/siteassets/files/jobs_and_training/warn/warn_report.xlsx)
Because there’s a penalty to pay for not reporting/giving a 60-day notice, my understanding is that employers would need to provide pay (severance) to employees, for 60 days, to bypass this penalty and not be held “accountable”. All that to say: if you’ve been working at the company for 120+ days and were given less than 60 days of severance, I’d look into this more.