Traditionally layoffs are done with no notice. I’ve been let go before, its just the way its done.
Whether or not a weeks severance is sufficient might be a question certainly, and that would depend on the local laws, contracts and traditions in the industry.
I’m sure that after the tantrum by the layoffees , the management is glad they did the firings as they did.
So, I ask, would management be glad to receive notices that employees are going to quit 5 minutes before the employees walk out the door?
Notice is a difficult situation in layoffs. In a perfect world, everyone would get sufficient notice and behave professionally prior to their departure.
In the real world, people are petty, they stop working, they steal and damage company property. One woman who was fired in my office walked over to the server, opened it up and ripped out all the wires, then threw coffee on the motherboard. She spent some time in jail when the cops went to her house to retrieve property she stole and found cocaine on her coffee table.