Let's review:

You work somewhere, and you accrue Sick and Vacation pay that you don't take. So, that component is from Working In NY, by definition. Then, they paid Severance, which is from the NY Job. These three types of payments are treated the same as Wages. The 2019 Wages are reported as from the NY job.

You stated:

"Taxpayer accepted early retirement/severance in December 2019.

Final payment (severance/unused vacation and sick days, etc)"

You never described that any part of the Final payment was other than these three components. Not Retirement payment.

I'm just evaluating what you told us. You seem to know what it is and what it isn't.

We don't always get to do what we would Like to do.