Even in California? (Series question I’m too lazy to Google)

He's offering 3 months to avoid violating the WARN act - so while severance is not required, following WARN is.

They don't need to offer severance, but they do (in many cases) have to offer a minimum 60 days notice of lay off. The initial wave of layoffs offered at least 60 days severance in lieu of notice. How this "love it or leave it" ploy works I'm not sure, but since there is severance, it probably doesn't matter.

The question now is, with no one in payroll department, will people laid off with a promised amount of severance pay ever see it?

The Federal Worker Adjustment and Retraining Notification Act or WARN Act, offers protection to workers, their families and communities by requiring employers (with 100 or more full-time workers) to provide written notice 60 days in advance of plant closings, mass layoffs and/or sale of a business.