"I thought only convenience states taxed regardless of where work is performed."

This?

"Connecticut, Delaware, Nebraska, New Jersey, New York, and Pennsylvania have a “convenience of the employer” rule, which states that if the employer requires the employee to work in another state (i.e., for the employer's convenience), then withholding is only taken in the location where the work is performed."

https://www.cpajournal.com/2021/08/20/remote-work-arrangements/