It's done on the scale of whatever time frame the management think the risk exists. In this case, if management thinks that risk exists for months - still acceptable.

While unusual, if management needs to end the employment of staff but is precluded in doing so by law.... the only thing Twitter must do is provide normal compensation & benefits, nothing else. Under employment contracts, the employee must do whatever the employee deems acceptable (within legal limits, or leave under their own will.)