It's a hard problem to solve, but given that many of the folks being dismissed are engineers with elevated access to Twitter's data and services, it makes sense from a security and privacy perspective to disable access first. There's no good way to lay off 300 people at once. Hopefully Twitter actually follows through on the separation package and job search assistance. That's far more important.

Do former twitter engineers really need that much assistance in finding a new job? I'd assume people will be clawing at them.

It may not show a lot of trust in their employees, but removing access is a prudent move considering the motive and opportunity for malfeasance. The timing should have been simultaneous however.