Strong disagree. For anyone who makes enough to be getting severance, it's better to have it in the new tax year.
Of course details vary country to country.
One fairly common thing is you can opt to take it as an lump sum now, or take it as a monthly salary - but with the proviso that if you take a new job you stop getting it. This is often the way benefit extensions work also. Sometimes the monthly option is larger.
So financially you are often better off with the lump sum, but it can be a tax hit.