You have to check NYS rulings in this. Like many states, NY doesn't want to give up the income.
Was the home office usage mandatory or optional? If optional, the employee can't get out of paying NYS tax.
May 15, 2006 is not that clear but NY is: https://www.tax.ny.gov/pit/file/nonresident-faqs.htm#telecommuting
My primary office is inside New York State, but I am telecommuting from outside of the state due to the COVID-19 pandemic. Do I owe New York taxes on the income I earn while telecommuting?
If you are a nonresident whose primary office is in New York State, your days telecommuting during the pandemic are considered days worked in the state unless your employer has established a bona fide employer office at your telecommuting location.
There are a number of factors that determine whether your employer has established a bona fide employer office at your telecommuting location. In general, unless your employer specifically acted to establish a bona fide employer office at your telecommuting location, you will continue to owe New York State income tax on income earned while telecommuting.