Understanding the NE5532's opamp input impedance
The input resistance in the NE5532 is the differential input resistance and not the resistance from either input pin to a supply rail. That's why it barely affects the circuit because, the inputs are generally at the same voltage - negative feedback ensures that. If you want to know what effect the common mode impedances have on the target circuit you will have to make do with bias current specifications.

Modern chips will usually specify both differential and common-mode input impedances but the NE5532 isn't a modern chip in any sense of the word.