handling layoffs
In CA the way silicon valley tech companies frequently handle layoffs is you're dismissed effective immediately, but still on payroll (including medical insurance, if any) for the aforementioned 60 days.
If the company is at all trying to appear graceful, they'll sometimes give additional time to the severance package, e.g. 1 week for every year of service at the company.
But in most cases the laid-off employee is no longer actively working at the company, access has usually been revoked, and so on. But WARN requirements have been satisfied.
Accrued expenses (like vacation hours and some other things) are also cashed-out to the departing employee. This, btw, is supposedly one motivation for some companies not tracking vacation time in favor of "unlimited vacation" -- it moves an accrued expense off the books and into informal "maybe never gets used" territory. YMMV.
Usually this "cashing out" maneuver is handled pretty promptly after the employee is notified of their impending separation; the company's motivation is presumably to clear the books and remove potential liabilities as quickly as possible. From the employee perspective, yes it may suck to be out of a steady paycheck, but they've been sent off with 60 days' pay to look for another job.
Seems odd that elon wouldn't just handle twitter layoffs the same way. If he isn't, perhaps he's assuming the rules (and laws) don't apply to him - there's apparently some history of that behavior.