New York Form IT-201 line 69a, NYC school tax credit, is a refundable credit. A refundable credit is treated as a payment. Tax withheld is also a payment. But not all payments are withholding. Line 76 is total payments, not total withholding. Only lines 72, 73, and 74 are tax withheld.
TurboTax treats it that way because that's how the state treats it.